Document text
31© World Health Organization
WHO Technical Report Series, No. 927, 2005
Annex 1
WHO guidelines on nonclinical
evaluation of vaccines
This document provides guidance to national regulatory authorities
(NRAs) and vaccine manufacturers on the nonclinical evaluation of vac-cines by outlining the international regulatory expectations in this area. Itshould be read in conjunction with the Guidelines on clinical evaluation ofvaccines: regulatory expectations (1), in order to complete the under-standing of the whole process of vaccine evaluation. Vaccines are
a diverse class of biological products and their nonclinical testing
programmes will depend on product-specific features and clinical indica-tions. The following text has therefore been written in the form of guide-lines rather than recommendations. Guidelines allow greater flexibilitythan recommendatisons with respect to specific issues related to particu-lar vaccines.
Introduction 32
1General remarks 32
1.1 Scope 34
1.2 Glossary 34
2Characterization of candidate vaccines 37
3Immunogenicity and other pharmacodynamic studies 43
4Toxicity assessment 44
4.1 Basic toxicity assessment 45
4.2 Additional toxicity assessments 48
5Special considerations 51
5.1 Adjuvants 51
5.2 Additives (excipients and preservatives) 52
5.3 Vaccine formulation and delivery device 52
5.4 Alternative routes of administration 53
6Specific considerations for particular types of vaccines 54
Authors 56
References 58
AppendixList of tissues to be collected in a repeated dose toxicity study 62
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32Introduction
Recent progress in biotechnology and basic immunology has led to
the development of a broad range of novel vaccines raising exciting
possibilities for the prevention of infectious diseases ( 2, 3). Improve-
ments to already licensed vaccines are also being considered; suchimprovements will lead to new products as well as to the introductionof new adjuvants. However, the complexity and novelty of these
products presents scientific and regulatory challenges because criteria
for their safety, potency and quality assessment may not exist. Prod-uct diversity and new approaches, technologies and methodologies
develop over time; therefore, judgement based on the best science
available should always form the basis for deciding on the type and
extent of nonclinical evaluation for these products.
Although nonclinical evaluation plays an essential part in the
overall development of vaccine candidates, there is at present limited
guidance regarding nonclinical evaluation programmes for theseproducts. In this guidance document, the general principles of
nonclinical evaluation of vaccines are discussed, with particular atten-
tion being given to the regulatory expectations for new and novel
vaccines.
Preclinical testing is a prerequisite to moving a candidate vaccine
from the laboratory to the clinic and includes all aspects of testing,
product characterization, proof of concept/immunogenicity studies
and safety testing in animals conducted prior to clinical testing of the
product in humans. Nonclinical evaluation, within the context of
this document, refers to all in vivo and in vitro testing performedbefore and during the clinical development of vaccines. For example,
nonclinical evaluation may be necessary when changes in the manu-
facturing process or product formulations are made or to further
study potential safety concerns that may have arisen from phase I
and II trials or that have been described in the literature for similarproducts.
1General remarks
Nonclinical studies are aimed at defining the in vitro and in vivo
characteristics of candidate vaccines including those relating to safety
and immunogenicity. Nonclinical studies in animals are valuable tools
for identifying possible risks to the vaccinees and helping to plan
protocols for subsequent clinical studies in human subjects. However,in all cases, when safety testing in animals is performed, there should
be a clear rationale for doing so and the study should be performed in
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33compliance with the national and international laws for the protection
of laboratory animals ( 4), biosafety requirements ( 5) and with good
laboratory practice (GLP) ( 6). However, there may be situations
where full compliance with GLP is not possible. If the study, or part
of the study, was not conducted in compliance with GLP, areas of
noncompliance should be defined and a statement of the reason for
noncompliance should be drawn up.
Potential safety concerns for a vaccine product include those due to
inherent toxicities of the product, toxicities of impurities and con-
taminants, and toxicities that result from interactions between the
vaccine components present in the vaccine formulation. In addition,the immune response induced by the vaccine may lead to toxic
side-effects.
Despite efforts to maximize the predictive value of nonclinical toxic-
ity studies there is always the possibility that not all risks are identi-
fied. The limitations of animal testing in reflecting clinical safety and
efficacy in humans should be recognized as pathogenesis and immune
responses are frequently species-specific. Moreover, potential safety
concerns identified during animal testing may not necessarily indicatea problem in humans. However, any signal observed in nonclinical
toxicity studies should be carefully addressed in human clinical trials
and may require additional nonclinical testing. It should be noted
that the absence of detectable toxicity in animal studies does not
necessarily mean a vaccine will be safe in humans. Potential safetyconcerns related to specific types of vaccine candidate are considered
in section 6.
The development and subsequent validation of in vitro tests for use as
alternatives to nonclinical evaluation of vaccine candidates in animals
is encouraged as it may lead to the improvement of nonclinical testing
as well as to a reduction of animal usage.
The need for and extent of nonclinical testing will depend on the
product under consideration. For example, for a product for whichthere is no prior nonclinical and clinical experience, nonclinical test-
ing would be expected to be more extensive than for those vaccines
previously licensed and used in humans. In some cases, it may not benecessary to perform preclinical safety studies prior to the initiation
of phase 1 clinical trials. For example, in the case of transfer of
technology, where access to the database of the originally developed
vaccine is available, data from nonclinical bridging studies (e.g. physi-
cochemical characterization and abbreviated in vivo studies) may bean acceptable basis for further development of the product.
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34Early communication between the vaccine manufacturer and the re-
sponsible national regulatory authority to agree on the requirements
for and type of nonclinical testing is recommended.
1.1 Scope
For the purposes of this document, vaccines are considered to be a
heterogeneous class of medicinal products containing immunogenic
substances capable of inducing specific, active and protective hostimmunity against infectious disease.
Although most vaccines are being developed for pre- and post-
exposure prophylaxis, in some cases, they may be indicated for thera-
peutic use against infectious diseases, e.g. human immunodeficiency
virus (HIV), and human papillomavirus (HPV). Both prophylactic
and therapeutic vaccines for infectious disease indications are consid-
ered in this document.
Vaccines for human use include one or more of the following: mi-
croorganisms inactivated by chemical and/or physical means that
retain appropriate immunogenic properties; living microorganisms
that have been selected for their attenuation whilst retaining
immunogenic properties; antigens extracted from microorganisms,secreted by them or produced by recombinant DNA technology;
chimeric microorganisms; antigens produced in vivo in the vaccinated
host following administration of a live vector or nucleic acid or anti-
gens produced by chemical synthesis in vitro. The antigens may be in
their native state, truncated or modified following introduction ofmutations, detoxified by chemical or physical means and/or aggre-
gated, polymerized or conjugated to a carrier to increase immunoge-
nicity. Antigens may be presented plain or in conjunction with an
adjuvant, or in combination with other antigens, additives and other
excipients.
Therapeutic vaccines for non-infectious diseases (e.g. certain cancer
vaccines) and monoclonal antibodies used as immunogens (e.g. anti-
idiotypic antibodies) are not considered here.
1.2 Glossary
The definitions given below apply to the terms used in these guide-lines. They may have different meanings in other contexts.
Adjuvants
Substances that are intended to enhance relevant immune response
and subsequent clinical efficacy of the vaccine.
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35Booster vaccination
Vaccination given at a certain time interval after primary vaccination
to enhance immune responses and induce long-term protection.
Combination vaccine
A vaccine that consists of two or more antigens, either combined bythe manufacturer or mixed immediately before administration and
intended to protect against either more than one disease, or against
one disease caused by different strains or serotypes of the same
organism.
Genetically modified organism (GMO)
An organism or a microorganism in which the genetic material hasbeen altered in a way that does not occur naturally by mating and/or
natural recombination. This definition covers microorganisms includ-
ing viruses, viroids and cell cultures including those from animals,but does not cover naked recombinant DNA or naked recombinant
plasmids.
Good clinical practice (GCP)
A standard for clinical studies that encompasses their design, conduct,monitoring, termination, audit, analyses, reporting and documenta-
tion and which ensures that the studies are scientifically and ethically
sound and that the clinical properties (diagnostic, therapeutic or pro-
phylactic) of the pharmaceutical product under investigation areproperly documented.
Good laboratory practice (GLP)
A quality system concerned with the organizational process and theconditions under which nonclinical health and environmental safety
studies are planned, performed, monitored, recorded, archived and
reported. GLP principles may be considered as a set of criteria to be
satisfied as a basis for ensuring the quality, reliability and integrity of
studies, the reporting of verifiable conclusions and the traceability ofdata.
Good manufacturing practice (GMP)
A part of the pharmaceutical quality assurance which ensures thatproducts are consistently produced and controlled according to the
quality standards appropriate to their intended use and as required by
the marketing authorization. In these guidelines, GMP refers to the
current GMP guidelines published by WHO.
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36Immunogenicity
Capacity of a vaccine to induce antibody-mediated and/or cell-
mediated immunity and/or immunological memory.
Nonclinical evaluation of vaccines
All in vivo and in vitro testing performed before and during clinical
development of vaccines. The potential toxicity of a vaccine should beassessed not only prior to initiation of human trials, but throughout
clinical development.
Plasmid
Double-stranded circular DNA molecules capable of replicating in
bacterial cells.
Potency
The measure of biological activity, using a suitable quantitative bio-
logical assay, based on the attribute of the product that is linked to the
relevant biological properties.
Preclinical evaluation of vaccine
All in vivo and in vitro testing carried out prior to the first testing of
vaccines in humans. This is a prerequisite to the initiation of clinical
trials and includes product characterization, proof of concept/immu-nogenicity studies and animal safety testing.
Preclinical toxicity study
A study designed with the primary purpose of demonstrating the
safety and tolerability of a candidate vaccine product. The design of
the preclinical toxicity study should meet the criteria outlined in the
section on study design to be considered supportive of the intended
clinical trial.
Primary vaccination
First vaccination or series of vaccinations given within a predefined
period, with an interval of less than 6 months between doses, to
induce clinical protection.
Product characterization
A full battery of physical, chemical and biological tests conducted fora particular product. These tests include, but are not limited to, in-
process control testing, testing for adventitious agents, testing process
additives and process intermediates, and lot release.
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37Protocol or study plan
A document that states the background, rationale and objectives of
the nonclinical studies and describes its design, methodology and
organization, including statistical considerations, and the conditionsunder which it is to be performed and managed.
Relevant animal model
An animal that develops an immune response similar to the expected
human response after vaccination. It is acknowledged that species-
specific differences in immune responses are likely. Ideally, the ani-
mal species chosen should be sensitive to the pathogenic organism or
toxin under consideration.
Route of administration
The means by which the candidate vaccine product is introduced tothe host. Possible routes of administration include the intravenous,
intramuscular, subcutaneous, transcutaneous, intradermal, trans-
dermal, oral, intranasal, intranodal, intravaginal and intrarectal
routes.
Seroconversion
Predefined increase in antibody concentration, considered to corre-
late with the transition from seronegative to seropositive, providing
information on the immunogenicity of a vaccine. If there are pre-
existing antibodies, seroconversion is defined as a transition from a
predefined low level to a significantly higher defined level, such as afourfold increase in geometric mean antibody concentration.
Validation
The action of proving, in accordance with the principles of good
manufacturing practice, that any procedure, process, equipment
(including the computer software or hardware used), material, activ-
ity or system actually leads to the expected results.
2 Characterization of candidate vaccines
2.1 Vaccine production
The biological nature of the starting materials, the manufacturing
process and the test methods needed to characterize batches of the
product are important elements to be considered in the design and the
interpretation of nonclinical testing of vaccines. Many vaccines areproduced using prokaryotic or eukaryotic microorganisms and subtle
changes in these organisms may radically affect the vaccine product.
Therefore, the establishment of a seed-lot system is essential for
vaccine production. Moreover, the quality, safety and potency of
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38these products are usually sensitive to changes in manufacturing
conditions. The quality and safety of vaccine preparations cannot be
assured solely by testing of the end-product, but depends on the strictcontrol of the manufacturing process following the principles of good
manufacturing practice (GMP) ( 7). This includes demonstration of
the purity and quality of the starting material (raw materials andseeds), in-process control testing, testing for process additives and
process intermediates and the development and establishment of lotrelease tests. Moreover, as the relationship between physical and
chemical characteristics, and the immunogenicity and efficacy of
these products is frequently not completely understood, biological
characterization through the use of biological assays should always
complement the physical and chemical product characterization. Thedevelopment of appropriate laboratory methods to characterize a
vaccine formulation with respect to its components, as well as its
safety and potency, is a prerequisite to the clinical use of any new or
novel vaccines against bacteria, viruses or parasites.
Consistency of production is essential, and the demonstration that the
product does not differ from vaccine lots that have been shown to be
safe and adequately immunogenic and protective in clinical studiesis a crucial component of vaccine evaluation, licensing and batch
release. For this reason, manufacturers should make every effort to
characterize these clinical lots and if possible to keep some of these
lots for future reference.
Where no appropriate animal model exists for testing potency or
where direct serological or immunological correlates of clinical pro-
tection are not available, the challenge is to ensure that each produc-
tion batch has the same protective efficacy as those batches shown to
be protective in clinical trials. In such cases, emphasis is increasinglybeing placed on assuring the consistency of production using modern
physical, chemical and immunological methods that enable character-
ization of some products to a degree of precision not previously
possible.
The vaccine lots used in preclinical studies should be adequately
representative of the formulation intended for use in the clinical
investigation and, ideally, preclinical testing should be done on thesame lot as that proposed for the clinical trials. If this is not feasible,
then the lots studied should be comparable with respect to physico-
chemical data, stability and formulation.
At a minimum, candidate vaccines for clinical trials should be pre-
pared under conditions of good manufacturing practice (GMP) for
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39clinical trial material ( 8). However full GMP will be required at the
later stages of clinical development ( 7, 9).
Any change proposed to the manufacturing process during vaccine
development should be considered carefully to evaluate its impact on
the quality, safety and efficacy of the vaccine and the possible need foradditional nonclinical and clinical investigations.
Subsequent changes in production methods or scale-up following
product licensure will necessitate further product characterization to
demonstrate comparability with the original lot(s) used to demon-
strate safety and efficacy of the product. The extent of comparabilitytesting needed depends on the nature of the changes implemented
(10). These changes should be documented and the national regula-
tory authority consulted. Regulatory authorities should clearly defineand implement in their regulations what changes require only a
notification and which changes require formal approval before imple-mentation ( 11).
The procedures used in the characterization and control of existinglicensed traditional vaccines are not likely to be applicable to newer
products developed using state-of-the-art technology to protect
against the same infection. For example, specific guidelines have beendeveloped for the production and control of acellular pertussis vac-
cines that differ from those applied to whole cell pertussis vaccine
(12). Likewise, the tests applied to the characterization and control of
traditional inactivated cholera vaccine for parenteral use are not nec-essarily applicable to the new inactivated whole-cell cholera vaccineintended for oral administration, and an appropriate potency test for
the oral vaccine needs to be developed.
2.2 Potency
Potency tests measure the biological activity of a vaccine but do not
necessarily reflect the mechanism of protection in humans. Potencymeasurement is often used to verify the consistency of the manufac-
turing process. The initial concept of potency testing for vaccines was
to quantify the biological activity of the vaccine in comparison with a
reference preparation of known bioactivity, where the antigenic
component(s) were not well-defined.
Classical challenge studies in animals immunized with the vaccine
under consideration have been developed into routine potency assays
(e.g. for diphtheria and tetanus toxoids). In the case of the whole-cell
pertussis potency assay, which consists of intracerebral challenge of
immunized and nonimmunized animals, a correlation was establishedwith clinical protection in humans ( 11). Where no suitable animal
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40challenge model exists, potency is often based on measurement of
immune responses, usually serological (e.g. influenza and hepatitis B
vaccines).
More recently, recombinant DNA methodology and modern physico-
chemical techniques have resulted in the manufacture of highly puri-fied products that can be better characterized than the classic
biologicals. However, the ability to measure the “relevant” biological
activity for such products may still be lacking. For these products,characterization using physicochemical parameters, such as amount
of antigen, size of the antigen, protein content and others can be used
as a measure of consistency, but not necessarily of the potency of a
vaccine.
For live attenuated vaccines, the approach to potency measurement is
generally different. The potency of live viral vaccines is usually based
on titration of the minimum infective dose in cell culture or chickenembryos, which may be considered as a surrogate marker of potency,
but not as a measure of potency itself. A similar approach is taken
to the potency measurement of live attenuated bacterial vaccines,
bacille Calmette–Guérin (BCG), and typhoid vaccine (live Ty21A
oral), where the number of live organisms present is the measure ofpotency.
For vaccines that express inserts encoding heterologous vaccine anti-
gens (vaccines based on viral or bacterial vectors), it is not sufficient
to determine the “biological activity” of the entire construct by mea-
suring colony forming units (CFU) or infectious titre. For thesevaccines, the use of other methods such as the quantitation of the
expression of the insert, or the evaluation of the effective dose (ED
50)
of the vectored vaccine should be considered.
2.3 Stability
The evaluation of vaccine stability is complex, as they are very suscep-
tible to inactivation by environmental factors. Potency, as defined in
the glossary, should be measured as a part of the stability testing,
except in those cases where potency testing based on biological activ-
ity is not possible. Physical and chemical product characterization
should be included in the stability evaluation. For a product enteringhuman clinical trials, sufficient data should be collected to support
the stability of the product for the duration of the preclinical and
clinical trial. In certain cases, accelerated stability data may be used to
support preliminary data obtained at the normal storage temperature.
Stability data to support licensure should be obtained under theproposed storage conditions and should be based on long-term,
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41real-time stability studies. Finally, the stability of standards and
reference materials also needs to be considered to ensure that the
procedures used to measure relevant parameters are reliablystandardized.
2.4 International and national guidelines
The World Health Organization (WHO), through considerable inter-national consultation, develops Recommendations and Guidelines
on the production and control of vaccines and other important
biologicals (13), and these form the basis for assuring the acceptability
of products globally. These documents specify the need for appropri-
ate starting materials, including seed lot system and cell banks; strictadherence to established protocols; tests for purity, potency, and
safety at specific steps during production; and the keeping of proper
records. Guidelines allow greater flexibility than Recommendations
with respect to specific issues related to particular vaccines.
WHO also provides Guidelines on manufacturing establishments in-
volved in vaccine production. Recommendations can be found in the
WHO document on good manufacturing practice for biologicals ( 7).
Particular attention should be given to developing documented stan-dard operating procedures for both production processes and testing
procedures. These should be introduced as early as possible duringthe development of a vaccine and be well established by the time
phase III clinical studies are undertaken and an application for mar-
keting authorization is filed. The basic principles for the production
and control of vaccines are published in the WHO Technical Report
Series (7, 14–18). Specific WHO guidelines and recommendations for
particular vaccines are also available and should be consulted where
appropriate.
WHO Recommendations and Guidelines are intended to be scientific
and advisory in nature and to provide guidance for national regula-
tory authorities and for vaccine manufacturers. These documents maybe adopted by national health authorities as definitive national regu-
lations or used as the basis of such regulations. They are also used as
the basis for deciding the acceptability of vaccines for purchase by
United Nations agencies such as the United Nations Children’s Fund
(UNICEF) for use in global immunization programmes. Regulatoryrequirements for vaccines and other biologicals are also produced by
other bodies, such as the European Agency for the Evaluation of
Medicinal Products (EMEA) and the US Center for Biologics Evalu-
ation and Research (CBER) (19); these documents can be found on
the appropriate web sites (www.emea.eu.int and www.fda.gov/cber).In addition, pharmacopoeial requirements, such as those of the
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42European Pharmacopoeia , are also established for vaccines and are
available at www.pheur.org.
For newly developed products, specific WHO, national or pharmaco-
poeial requirements may not be available and a national regulatory
authority will need to agree on specifications with the manufactureron a case-by-case basis during the evaluation of products for clinical
trials and for licensing. For some of these novel products general
guidance on production and control from WHO can be found inrelevant documents, such as those describing DNA and peptide vac-
cines ( 14, 16), as well as recommendations on animal cell substrates
used for production of biologicals ( 14).
In addition, information on how to assure the quality of biologicals in
general and on procedures for approving manufacture and for setting
up a national control laboratory, can be found in the relevant WHO
guidelines ( 17, 18). For a vaccine intended to be marketed worldwide,
the development of which also involves much international collabora-
tion, it will be essential to ensure consistency of a regulatory approach
for novel products such as vaccines for HIV prevention ( 19).
2.5 Batch release and independent laboratory evaluation
The potential variability of methods for the production of biologicalshas led to the establishment of national and international require-
ments to define procedures for assuring the quality of vaccines and
for assessing consistency both among manufacturers and over longperiods of time. Licensed vaccines are subject to independent batch
release (review, testing and authorizing release of a batch of vaccine
independent of the manufacturer) by a national regulatory authority
or national control laboratory, before release on to the market. Inde-
pendent evaluation entails at least an evaluation of a manufacturer’sbatch release data (protocol review), but in many instances it also
includes independent laboratory testing in addition to that carried out
by the manufacturer.
Batch or lot release tests are those tests chosen during full product
characterization to demonstrate the purity, safety and potency of
the product. Lot release testing provides one measure of assurance
that a lot can be manufactured consistently. Validation and establish-ment of lot release tests and specifications is a process that continues
throughout product development and should be finalized prior to
licensure.
In some countries, samples of vaccine for clinical trials are required by
the national regulatory authority, as a part of the approval process forclinical trials. Vaccine developers are encouraged to consult the
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43appropriate regulatory agency early on during the development of a
vaccine.
2.6 Standards and reference materials
Standards and reference materials play a vital part in the licensing andquality control process, their role ranging from use in specific antigen
recognition tests to assays of vaccine toxicity, immunogenicity and
potency. The standardization of the methods used to evaluate vac-
cines, as well as those used to evaluate immune responses to vaccineantigens, is also vital so that results may be compared directly be-
tween laboratories both within and between countries, and between
clinical trials.
WHO International Biological Standards and Reference Reagents
are the primary standards in use worldwide. In addition, nationalregulatory authorities and manufacturers may establish secondary
(regional, national), working standards for the purpose of testing
vaccine quality on a lot-to-lot basis. Such standards should be cali-
brated against International Standards, when they exist. There is
concern that different secondary standards may result in “drifting”from the International Standard. Production of secondary standards
on a large scale (e.g. on a regional basis) reduces the number of
secondary standards in use, and should improve accuracy of testing
vaccine quality. For example, the European Department for the
Quality of Medicines of the Council of Europe, has been active inestablishing working standards for vaccines that are calibrated against
the WHO International Standards, where appropriate. The complete
list of WHO International Standards and Reference Reagents can befound on the WHO web site at: www.who.int/ biologicals.
3Immunogenicity and other pharmacodynamic studies
A pharmacodynamic study for a vaccine product is generally con-
ducted to evaluate the immunogenicity. However, a pharmacody-
namic study may also extend to include the pharmacology of an
adjuvant.
Immunization studies in animal models should be conducted because
they may provide valuable “proof of concept” information to supporta clinical development plan. In addition, immunogenicity data de-
rived from appropriate animal models are useful in establishing the
immunological characteristics of the product and may guide selection
of the doses, schedules and routes of administration to be evaluated
in clinical trials. Nonclinical immunogenicity studies should assessthe relevant immune response, e.g. humoral and/or cell-mediated
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44immune response, induced in the vaccinated animals. Depending on
the immune response induced, such studies may include an evaluation
of seroconversion rates, geometric mean antibody titres, or cell-mediated immunity in vaccinated animals. Nonclinical studies should,
where possible, be designed to assess relevant immune responses,
including functional immune response (e.g. neutralizing antibodies,
opsonophagocytic activity, etc.) leading to protection. These studies
may also be designed to address interference between antigens and/orlive viruses. If a vaccine consists of more than one defined antigen
(e.g. acellular pertussis vaccine consisting of 3–5 protein products) the
response to each antigen should be evaluated. Where appropriate,
challenge/protection studies with the corresponding infectious agent
may be conducted to confirm the relevance of the animal models.A primary concern in interpreting the data obtained from such studies
should be to determine how closely the animal model resembles the
disease and immune response in humans. It should be recognized that
animal models frequently fail to predict immunogenicity and efficacy
in humans.
4Toxicity assessment
The nonclinical safety assessment of vaccines needs to be viewed in
the context of the evolving field of vaccine development. Thus, judge-
ment based on the best science available should always form the basisfor any decisions regarding the need for nonclinical safety studies,
types of study and study designs. Similarly, scientific judgement
should be applied to the interpretation of data from preclinical stud-
ies, regarding the risk–benefit ratio, animal model, dosing etc. For
example, the observation of hypersensitivity reactions in an animalmodel may not necessarily preclude proceeding to clinical trials, but
may indicate the necessity for careful monitoring of a particular clini-
cal parameter.
Section 4.1 provides a general framework for designing a preclinical
toxicity study for a vaccine. The parameters set out in this section areconsidered the minimum necessary for a safety assessment prior to
the initiation of clinical trials in humans, in situations where preclini-
cal safety studies are deemed necessary. As the design of any toxicity
study is product-specific and based on indications, modifications to
the framework outlined below may be necessary in response to par-ticular product features, availability of animal models, methodolo-
gies, etc.
Section 4.2 provides additional considerations for performing
special toxicity assessments that may be required on a case-by-case
basis.
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454.1 Basic toxicity assessment
4.1.1 Study design
The preclinical toxicity study should be adequate to identify and
characterize potential toxic effects of a vaccine to allow investigators
to conclude that it is reasonably safe to proceed to clinical investiga-
tion. The parameters to be considered in designing animal toxicologystudies are the relevant animal species and strain, dosing schedule and
method of vaccine administration, as well as timing of evaluation of
end-points (e.g. sampling for clinical chemistry, antibody evaluation
and necropsy). The route of administration should correspond to
that intended for use in the clinical trials. When the vaccine is tobe administered in human clinical trials using a particular device, the
same device should be used in the animal study, where feasible (e.g.
measles aerosol vaccine in the monkey model). Potential toxic effects
of the product should be evaluated with regard to target organs, dose,
route(s) of exposure, duration and frequency of exposure, and poten-tial reversibility. The toxicity assessment of the vaccine formulation
can be done either in dedicated-stand alone toxicity studies or in
combination with studies of safety and activity that have toxicity end-points incorporated into the design. The study should also include an
assessment of local tolerance.
4.1.2 Animal species, sex, age and size of groups
Data to be recorded on the animals used for toxicity testing shouldinclude information on the source, species and animal husbandry
procedures (e.g. housing, feeding, handling and care of animals). Ingeneral, the use of outbred animals is recommended. The health of
the animal will need to be evaluated in accordance with acceptable
veterinary medical practice to ensure that animals are free of any
condition that might interfere with the study. For instance, individual
housing of laboratory animals may be required to minimize the risk ofcross-infection.
Where possible, the safety profile of a product should be character-
ized in a species sensitive to the biological effects of the vaccine being
studied. Ideally, the species chosen should be sensitive to the patho-
genic organism or toxin. The animal species used should develop animmune response to the vaccine antigen. In general, one relevant
animal species is sufficient for use in toxicity studies to support initia-
tion of clinical trials. However, there may be situations in which two
or more species may be necessary to characterize the product, for
example where the mechanism of protection induced by the vaccine isnot well understood (for example, intranasal influenza vaccine and
intranasal measles vaccine).
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46In addition, when species-specific or strain-specific differences in the
pharmacodynamics of the product are observed, it may be necessary
to address the nonclinical safety of the product in more than onesafety study and in more than one animal model.
The size of the treatment group depends on the animal model chosen.
The number of animals used in studies using non-human primates
would be expected to be less than that in studies that used rodents.
For small animal models, e.g. rats and mice, it is recommended thatapproximately 10 males + 10 females per group be studied.
In general, the approximate age at the start of the study for rodents is6–8 weeks, and for rabbits, 3–4 months.
4.1.3 Dose, route of administration and control groups
The toxicity study should be performed using a dose that maximizesexposure of the animal to the candidate vaccine and the immune
response induced, for example, peak antibody response. In general,
an evaluation of the dose–response is not required as part of the basictoxicity assessment and the lethal dose does not have to be deter-
mined. However, pilot dose–response studies may be conducted to
determine which dose induces the highest antibody production in the
animal model. If feasible, the highest dose (in absolute terms) to be
used in the proposed clinical trial should be evaluated in the animalmodel. However, the dose is sometimes limited by the total volume
that can be administered in a single injection, and guidelines on
animal welfare should be followed. In such cases, the total volume
may be administered at more than one site using the same route of
administration. Alternatively, a dose that exceeds the human dose ona mg/kg basis and that induces an immune response in the animal
model may be used. In such cases, the factor between human and
animal dose should be justified.
The number of doses administered to the test animals should be equal
to or more than the number of doses proposed in humans. To bettersimulate the proposed clinical usage, vaccine doses should be given at
defined time intervals rather than as daily doses; the dosing interval
used in the toxicity study may be shorter (e.g. an interval of 2–3
weeks) than the proposed interval in clinical trials in humans. The
dosing interval in nonclinical trials may be based on the kinetics of theprimary and secondary antibody responses observed in the animal
model. A single-dose study may be performed in situations in which
vaccine-induced antibodies are expected to neutralize a live viral
vector, thus limiting the expression of the gene of interest (e.g. anti-
adenovirus immune response), or when immune responses induced in
FDA-CBER-2021-5683-1148931
47animals are expected to react with species-specific proteins present in
the vaccine formulation (e.g. human recombinant cytokines used as
adjuvants).
The route of administration should correspond to that intended for
use in the human clinical trials. If toxic effects are observed in safetystudies using a particular route of administration (e.g. intranasal),
further toxicity studies using a different route of administration (e.g.
intravenous) may be helpful in understanding the full spectrum oftoxicity of the product.
The study design should include a negative control group(s) to evalu-
ate a baseline level of treatment. If appropriate, active control groups
(e.g. vaccine formulation without antigen) may also be included in the
study. The study should include an additional treatment group of
animals to be killed and evaluated as described below at later time-
points after treatment, to investigate the reversibility of any adverseeffects observed during the treatment period and to screen for pos-
sible delayed adverse effects.
4.1.4 Parameters monitored
Toxicity studies should address the potential of the product for caus-
ing local inflammatory reactions, and possible effects on the draining
lymph nodes, systemic toxicity and on the immune system. A broad
spectrum of information should be obtained from the toxicity studies.Parameters to be monitored should include daily clinical observa-
tions, weekly body weights and weekly food consumption. During
the first week of administration frequent measurements of body
weight and food consumption are recommended, if feasible, as these
are sensitive parameters indicating “illness”. Interim analysis ofhaematology and serum chemistry should be considered approxi-
mately 1–3 days following the administration of the first and last dose
and at the end of the recovery period. Haematology and serum chem-
istry analyses should include, at the minimum, an evaluation of rela-
tive and absolute differential white blood cell counts (lymphocytes,monocytes, granulocytes, abnormal cells) and albumin/globulin ratio,
enzymes and electrolytes. In some cases, it may also be useful to
evaluate coagulation parameters, urine samples and serum immuno-
globulin classes. Data should be collected not only during treatment,
but also following the recovery phase (e.g. 2 weeks or more followingthe last dose) to determine persistence, and look at exacerbation
and/or reversibility of potential adverse effects.
At study termination, final body weights (after a period of fasting)
should be measured. Terminal blood samples should be collected and
FDA-CBER-2021-5683-1148932
48serum chemistry, haematology and immunological investigations
should be done as described in the preceding paragraph. The immune
response induced by the candidate vaccine should be assessed inorder to confirm that the relevant animal model has been selected. A
complete gross necropsy should be conducted and tissues collected
and preserved, gross lesions should be examined and organ weights
recorded ( 23). Histopathological examinations of tissues should
be performed and special attention paid to the immune organs, i.e.
lymph nodes (both local and distant from site of administration),
thymus, spleen, bone marrow and Peyer’s patches or bronchus-
associated lymphoid tissue, as well as organs that may be expected to
be affected as a result of the particular route of administration chosen.
Histopathological examinations should always include pivotal organs(e.g. brain, kidneys, liver and reproductive organs) and the site of
vaccine administration. The choice of tissues to be examined (ranging
from a short list limited to immune and pivotal organs to a full list
as provided in the Appendix) will depend on the vaccine in ques-
tion, and the knowledge and experience obtained from previousnonclinical and clinical testing of the vaccine components. For ex-
ample, full tissue examination will be required in the case of novel
vaccines for which no prior nonclinical and clinical data are available.Therefore, the list of tissues to be tested should be defined on a case-
by-case basis, following consultation with the relevant regulatory au-
thority. Data should be reported in full listing the original collection
of values, and summarized.
4.1.5 Local tolerance
The evaluation of local tolerance should be conducted either as a part
of the repeated dose toxicity study or as a stand-alone study. Toler-ance should be determined at those sites that come into contact with
the vaccine antigen as a result of the method of administration, and
also at those sites inadvertently exposed (e.g. eye exposure during
administration by aerosol) to the vaccine. More details have been
published elsewhere ( 24).
If abnormalities are observed in the basic toxicity study outlined in
section 4.1., further studies may be necessary to evaluate the mecha-
nism of the toxic effect.
4.2 Additional toxicity assessments
4.2.1 Special immunological investigations
In certain cases, the results from evaluations of immune response
from nonclinical and clinical studies, or from data on natural disease,
may indicate immunological aspects of toxicity, e.g. precipitation of
FDA-CBER-2021-5683-1148933
49immune complexes, humoral or cell-mediated immune response
against antigenic determinants of the host itself as a consequence of
molecular mimicry or exacerbation of the disease (e.g. inactivatedmeasles vaccine). In such cases, additional studies to investigate the
mechanism of the effect observed might be necessary.
Great similarity of vaccine determinants and host molecules could
cause autoimmune reactions induced by molecular mimicry ( 26).
Therefore, any vaccine antigen whose characteristics might mimic
those of a host antigen should be treated with caution, even though it
is recognized that molecular mimicry does not necessarily predispose
to autoimmunity.
Because considerable efforts may be required in selecting and devel-
oping relevant animal models to address the above issues, caution
should be exercised and a strong rationale provided when developing
vaccines for diseases associated with autoimmune pathology.
If data suggest that the pathogen against which the vaccine is directed
may cause autoimmune pathology, studies may be needed to address
this concern on a case-by-case basis, if an appropriate animal model
exists.
It should be noted that observations of biological markers for auto-
immune reactions are not necessarily linked to pathogenic conse-
quences. For instance, the presence of autoimmune antibodies doesnot necessarily indicate the induction of autoimmune disease ( 25).
When hypersensitivity reactions induced by the antigen(s), adjuvants,excipients or preservatives are of concern, additional investigations
may be warranted.
4.2.2 Developmental toxicity studies
Developmental toxicity studies are usually not necessary for vaccinesindicated for immunization during childhood. However, if the target
population for the vaccine includes pregnant women and women ofchildbearing potential, developmental toxicity studies should be con-
sidered, unless a scientific and clinically sound argument is put for-
ward by the manufacturer to show that conducting such studies isunnecessary. For a preventive vaccine, reproductive toxicity assess-
ments are generally restricted to prenatal and postnatal developmen-
tal studies, because the primary concern is any potential untoward
effect on the developing embryo, fetus or newborn. The need to
conduct fertility and post-weaning assessments should be consideredon a case-by-case basis. The animal model chosen should develop
FDA-CBER-2021-5683-1148934
50an immune response to the vaccine, which is usually determined by
serum antibody measurements. In addition, it is important to evaluate
maternal antibody transfer by measuring vaccine-induced antibodyin cord or fetal blood to verify exposure of the embryo or fetus to
maternal antibody. The route of administration should mimic the
clinical route of administration. Ideally, the maximal human dose
should be administered to the test animal. If it is not possible to
administer the full human dose, e.g. limitations on the total volumethat can be administered, or if local toxicity is observed that may
result in maternal stress, a dose that exceeds the human dose on a
mg/kg basis and is able to induce an immune response in the animal
should be used.
To assess any potential adverse effects of the vaccine during the
period of organogenesis, the gestating animal is usually exposed to
the vaccine during the period from implantation until closure of the
hard palate and end of gestation defined as stages C, D and E in the
ICH S5a document ( 27). Because of the relatively short gestation
period of most animal models used, pre-mating treatment is fre-
quently required to ensure maximal exposure of the embryo or fetus
to the vaccine-induced immune response. For a preventive vaccine,
the number of doses administered depends on the time of onset and
duration of the response. Booster immunizations may be necessary at
certain times during the period of gestation to maintain a high level ofantibody throughout the gestation period and to expose the develop-
ing embryo to the components of the vaccine formulation. End-points
include, but are not limited to, viability, resorptions, abortions, fetal
body weight and morphology. The reader is referred to other publica-
tions for guidance on end-points used to evaluate potential toxiceffects of the product on development of the embryo or fetus ( 27). It
is also recommended that a period of postnatal follow-up of pupsfrom birth to weaning be incorporated in the study design to assess
normality of growth, body weight gain, suckling activity and viability.
Studies should therefore be designed so that test groups are dividedinto subgroups. Half of the animals should be delivered by Caesarean
section and the other half allowed to deliver their pups without surgi-
cal intervention.
4.2.3 Genotoxicity and carcinogenicity studies
Genotoxicity studies are normally not needed for the final vaccineformulation. However, they may be required for particular vaccine
components such as novel adjuvants and additives. If needed, the in
vitro tests for mutations and chromosomal damage should be doneprior to first human exposure. The full battery of tests for genotoxicity
may be performed in parallel with clinical trials ( 28).
FDA-CBER-2021-5683-1148935
51Carcinogenicity studies are not required for vaccine antigens. How-
ever, they may be required for particular vaccine components such as
novel adjuvants and additives.
4.2.4 Safety pharmacology
The purpose of safety pharmacology is to investigate the effects of thecandidate vaccine on vital functions. If data from nonclinical and/or
human clinical studies suggest that the vaccine (e.g. one based on
specific toxoids) may affect physiological functions (e.g. central
nervous system, respiratory, cardiovascular and renal functions)
other than those of the immune system, safety pharmacology studiesshould be incorporated into the toxicity assessment. Useful informa-
tion on this topic can be found in the Note for Guidance on safety
pharmacology studies for human pharmaceuticals (29).
4.2.6 Pharmacokinetic studies
Pharmacokinetic studies (e.g. for determining serum or tissue concen-trations of vaccine components) are normally not needed. The need
for specific studies should be considered on a case-by-case basis (e.g.when using novel adjuvants or alternative routes of administration)
and may include local deposition studies that would assess the reten-
tion of the vaccine component at the site of injection and its further
distribution (e.g. to the draining lymph nodes). Distribution studies
should be considered in the case of new formulations, novel adjuvantsor when alternative routes of administration are intended to be used
(e.g. oral or intranasal).
5Special considerations
5.1 Adjuvants
Adjuvants may be included in vaccine formulations or co-
administered with vaccines to enhance the immune responses to par-ticular antigen(s), or to target a particular immune response. It is
important that the adjuvants used comply with pharmacopoeial re-
quirements where they exist, and that they do not cause unacceptable
toxicity.
Adjuvant activity is a result of many factors and the immune response
obtained with one particular antigen/adjuvant formulation cannot, as
a rule, be extrapolated to another antigen. Individual antigens vary intheir physical and biological properties and antigens may interact
differently with an adjuvant. Adjuvants must be chosen according to
the type of immune response desired and they must be formulated
with the antigen in such a way that distribution of both is optimized to
ensure availability to the relevant lymphatic tissues. The route of
FDA-CBER-2021-5683-1148936
52administration of the vaccine is also an important factor influencing
the efficacy and safety of an adjuvant.
The effect of the adjuvant should be demonstrated in preclinical
immunogenicity studies. If no toxicological data exist for a new adju-
vant, toxicity studies of the adjuvant alone should first be performed.In general, assessment of new or novel adjuvants should be under-
taken as required for new chemical entity ( 30–32). These data may be
obtained by the vaccine manufacturer or by the producer of the
adjuvant. In addition to assessing the safety of the adjuvant by itself it
is also important to assess whether the combination of antigen and
adjuvant exerts a synergistic adverse effect in the animal model
(33, 34). When species-specific proteins (e.g. cytokines) are used as
novel adjuvants, the issue of species-specific response should be
considered.
When evaluating the safety profile of the combination of adjuvant
and vaccine, the formulation proposed for clinical use should be
used.
Compatibility of the adjuvant(s) (e.g. lack of immune interference)
with all antigenic components present in the vaccine should be
evaluated.
If applicable, adsorption of all antigenic components present in the
vaccine should be shown to be consistent on a lot-to-lot basis. Poten-tial desorption of antigen during the shelf-life of the product should
be performed as a part of stability studies, the results reported and
specifications set, as this may affect not only immunogenicity, but alsothe toxicity profile of the product.
It should be noted that no adjuvant is licensed in its own right, but
only as a component of a particular vaccine.
5.2 Additives (excipients and preservatives)
Where a new additive is to be used, for which no toxicological dataexist, toxicity studies of the additive alone should first be performedand the results documented according to the guidelines for new
chemical entities ( 31). The compatibility of a new additive with all
vaccine antigens should be documented together with the toxicologi-cal profile of the final vaccine formulation under consideration in
animal models as outlined in section 4.
5.3 Vaccine formulation and delivery device
The vaccine formulation (i.e. liquid form, capsules or powder), as
well as the delivery device, may have an impact on the uptake of
FDA-CBER-2021-5683-1148937
53the vaccine, its effectiveness and safety. Ideally, the delivery device
and vaccine formulation tested in an animal safety study should be
identical to those intended to be used clinically. However, animalmodels in which delivery devices intended for clinical use can be
tested may not be available. In these instances, in order to develop an
appropriate animal model, it may be necessary to conduct pilot stud-
ies to define and optimize the conditions for drug delivery in the
animal model before it can be used to assess the preclinical safety ofthe product.
5.4 Alternative routes of administration
When using a vaccine formulation administered by alternative routes
(e.g. intranasal, oral, intradermal, rectal and intravaginal routes), it
can be assumed that their potency, relevant immunogenicity, toler-ability, toxicity, and long-term safety may differ from that of products
delivered by the parenteral route. Thus, when different routes of
administration are proposed, nonclinical safety studies may have tobe conducted using vaccine formulation and/or adjuvant alone in a
suitable animal model to address the specific safety concerns associ-
ated with vaccine administration by these routes. Particular issues
relevant to vaccines administered using alternative routes that may
need to be considered are discussed below.
5.4.1 Animal models
A special consideration for vaccines administered by alternative
routes should be the anatomy and physiology of the site of vaccine
administration of the particular animal model chosen and its accessi-bility for the administration of the vaccine. For example, for intra-
nasally administered products, the species chosen should ideally be
receptive to spray administration of the product. In general, rabbitsand dogs are useful test models for use of spray devices; however,
their olfactory bulbs are highly protected and special techniques
would be required to ensure that the test product reached this organ.
Although mice and rats are useful models, intranasal administration
to these species presents technical difficulties. Intranasal administra-tion to non-human primates may be preferable, if they are susceptible
to the infectious agent in question.
Depending on the level of concern regarding a particular route of
administration or when there are species-specific differences between
the animal models in their sensitivity to the candidate vaccine, it may
be necessary to address the preclinical safety of the product in more
than one safety study and in more than one animal model.
FDA-CBER-2021-5683-1148938
545.4.2 Dose
As the optimal dose derived from studies using the parenteral
route of administration may differ from the dose used for alternative
route(s) of administration, dose-finding studies may need to be con-ducted for a particular route of administration. Also, consideration
should be given to the total volume of the vaccine administered as it
may affect the outcome of the safety study. For example, intranasal
administration of more than 5 ml of test preparation per nostril to a
mouse would result in the test preparation being swallowed, rather
than being adsorbed by the nasal mucosa.
5.4.3 End-points
The toxicity end-points would include those described in section 4 andmay include additional outcome measures that would depend on the
route of administration and specific concerns associated with the par-
ticular route and target organ. For example, if there is concern aboutthe potential passage of vaccine components to the brain following
intranasal administration, immunohistology and “in situ” methods
and/or neurological assays and examinations may be necessary. For
vaccines administered by inhalation, outcome measures may include
pulmonary function tests and data on histopathology of the lungs.Considerable efforts may be required to develop appropriate meth-
ods to address potential safety concerns associated with the use of
new routes of administration.
5.4.4 Immunogenicity assessment
The development of appropriate assays for measuring mucosal im-mune responses is critical for vaccines that are expected to function asmucosal immunogens because serological assays alone may not reflect
the relevant immune response for a mucosal vaccine. Thus, in addi-
tion to measuring serological responses, it may be necessary to evalu-
ate T cell responses, antibody-secreting cells and cytokine production.
In addition, assays may need to be developed to assess the inductionof local and systemic responses at sites distant from administration of
the vaccine antigen.
6Specific considerations for particular types of vaccines
In addition to the testing strategies outlined in sections 3, 4 and 5,
studies may be necessary to address specific safety concerns associ-
ated with particular product types using suitable in vitro and in vivo
test methods. The specific testing requirements for live attenuatedand combination vaccines are discussed below. Detailed information
regarding the production and control of other types of vaccine is
available in the WHO guidance documents for production and con-
FDA-CBER-2021-5683-1148939
55trol (13), and should be consulted. For example, in the recently devel-
oped guidelines for DNA (16) and synthetic peptide vaccines (18, 35),
as well as for particular vaccines such as Hib conjugated vaccine (26),the issues relevant for nonclinical testing are discussed and should be
considered in the development of an appropriate design for the
nonclinical study of the vaccine in question.
6.1 Live attenuated vaccines
An assessment of the degree of attenuation, and the stability ofthe attenuated phenotype, are important considerations for the
nonclinical testing programme of a live attenuated vaccine. Labora-
tory markers of attenuation are invaluable for this purpose. Thesemarkers should be capable of distinguishing the attenuated vaccine
from fully virulent wild-type strains and, ideally, of detecting partial
reversion to full virulence. To assess the stability of the attenuation
phenotype, the vaccine may be passaged under production conditions
beyond the maximum passage number to be used for production.Stability of attenuation may also be assessed by passage under condi-
tions that are outside the conditions to be used for vaccine produc-
tion. For example, higher or lower temperatures may exert selection
pressure for reversion to virulence. The marker(s) of attenuation may
subsequently be used to qualify new vaccine seed preparations and tomonitor the effect of any significant changes in production conditions
of the attenuated phenotype.
If the wild-type organism is neurotropic, or if passages through neural
tissue have been used in the attenuation of a virus vaccine, then a test
for neurovirulence should be performed at least at the level of thevaccine seed. A neurovirulence test is not necessarily required for
all live attenuated vaccines. The specifications for an appropriate
neurovirulence test depend on the organism under test and should
be capable of distinguishing the attenuated vaccine from fully viru-
lent wild-type strains and, ideally, of detecting partial reversion tofull virulence. Specific reference preparations may be needed for
this purpose. Neurovirulence tests in small animal models may be
acceptable.
If the live attenuated vaccine is based on a genetically modified organ-
ism, then an environmental risk assessment may be required as part ofthe preclinical evaluation. An investigation into the possible shedding
of vaccine organisms following administration contributes to the envi-
ronmental risk assessment. For all live attenuated vaccines, infor-
mation on the likelihood of exchange of genetic information withnon-vaccine strains may be required and suitable nonclinical testsmay be designed to provide data for this purpose.
FDA-CBER-2021-5683-1148940
566.2 Combined vaccines
New combinations produced either by formulation or at the time of
reconstitution of antigens or serotypes should be studied for ap-
propriate immunogenicity in an animal model, if available, before
initiation of human clinical trials ( 36, 37). Combined antigens should
be examined by appropriate physicochemical means to evaluate
possible changes to antigen properties on combination, such as degree
of adsorption to aluminium adjuvants, as well as stability of the
combination.
The immune response to each of the antigens in the vaccine should be
assessed, including the quality of response and any potential interfer-
ence and incompatibilities between combined antigens. It is prefer-
able to study a new combination in comparison with the individual
antigens in animals to determine whether augmentation or diminu-
tion of response occurs.
The need to evaluate the safety of the new combination in an animal
model should be considered on a case-by-case basis. Such evaluationis likely to be necessary if there is concern that combining antigens
and/or adjuvants may lead to problems of toxicity (e.g. novel
adjuvant).
Similar consideration for nonclinical testing will also apply to cases
where a new candidate single-component vaccine is developed froman already licensed combined vaccine (e.g. monovalent oral polio
vaccine versus trivalent oral polio vaccine).
Authors
The first draft of these Guidelines on preclinical evaluation of vaccines was pre-
pared by the members of the WHO drafting group following the meeting held at theNational Institute of Public Health and the Environment (RIVM), the Netherlands14–15 March 2002 attended by:
Dr M. Gruber, Scientific Reviewer, Division of Vaccines and Related Products
Application, Center for Biologics Evaluation and Research, Food and Drug Admin-istration, Rockville, MD, USA; Dr A. Homma, Bio-Manguinhos Oswaldo Cruz Foun-dation, Rio de Janeiro, Brazil; Dr J.G. Kreeftenberg, Bureau for InternationalCooperation, National Institute of Public Health and the Environment, Bilthoven, theNetherlands; Dr J.W. van der Laan, National Institute of Public Health and theEnvironment, Bilthoven, the Netherlands; Dr E. Griffiths, Coordinator, QualityAssurance and Safety of Biologicals, World Health Organization, Geneva, Switzer-
land; Dr I. Knezevic, Quality Assurance and Safety of Biologicals, World Health
Organization, Geneva, Switzerland.
A second draft was prepared following a discussion on special immunological
considerations held at Agence Française de Sécurité Sanitaire des Produits de
FDA-CBER-2021-5683-1148941
57Santé, Lyon, France, 17 June 2002 attended by the following: Dr F. Fuchs, Agence
Française de Sécurité Sanitaire des Produits de Santé, Lyon, France; Dr D. Masset,Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSAPS), StDenis, France; Dr C. Ratignier Agence Française de Sécurité Sanitaire desProduits de Santé, St Denis, France; Dr Marc Pallardy, Agence Française deSécurité Sanitaire des Produits de Santé (AFSSAPS), St Denis, France, and afurther meeting of drafting group held in Geneva from 1–2 July 2002.
A third draft was prepared by the drafting group after an informal WHO Consulta-
tion on preclinical evaluation of vaccines: regulatory expectations, held in Geneva
from 12–13 December 2002, attended by the following participants:
Dr T. Bektimirov, Deputy Director, Tarasevic State Research Institute for Standard-
ization and Control of Medical Biological Preparations, Moscow, Russian Federa-tion; Dr E. Chaves Leal, Vice Director, Instituto Nacional de Control de QualidadSaude, Rio de Janeiro, Brazil; Dr W. Egan, Acting Director, Office of VaccinesResearch and Review, Center for Biologics Evaluation and Research, Food andDrug Administration, Rockville, MD, USA; Dr E. Griffiths, Associate Director General,Biologics and Genetic Therapies, Health Canada, Ottawa, Canada; Dr M. Gruber,Scientific Reviewer, Division of Vaccines and Related Products Application, Centerfor Biologics Evaluation and Research, Food and Drug Administration, Rockville,MD, USA; Dr M. Haase, Paul Ehrlich Institute, Langen, Germany; Dr A. Homma,Developing Country Vaccine Manufacturer’s Network, c/o Bio-ManguinhosOswaldo Cruz Foundation, Rio de Janeiro, Brazil; Dr J.G. Kreeftenberg, Bureau forInternational Cooperation, National Institute of Public Health and the Environment,Bilthoven, the Netherlands; Dr J.W. van der Laan, National Institute of Public Healthand the Environment, Bilthoven, the Netherlands; Dr R. Leke, Department ofImmunology and Microbiology, Faculty of Medicine, University of Yaounde,
Yaounde, Cameroon; Dr Lei Dianliang, Deputy Director, National Institute for the
Control of Pharmaceutical and Biological Products, Beijing, People’s Republic ofChina; Dr Lazara Martínez Muñoz, Centro para el Control Estatal de la Calidad de losMedicamentos, Havana, Cuba; Dr D. Masset, Agence française de SécuritéSanitaire des Produits de Santé, Saint-Denis, France; Dr R. Mignolet, RLM Consult-ing, Wavre, Belgium; Dr P. Minor, Head, Division of Virology, National Institute forBiological Standards and Control, Potters Bar, Herts., England; Dr G. Orefici, IstitutoSuperiore di Sanità, Rome, Italy; Dr M. Pallardy, Agence Française de SécuritéSanitaire des Produits de Santé, Veille Toxicologique/Vigilance, St Denis, France; DrJ. Petricciani, Carlsbad, USA; Dr P. Pitisuttithum, Vaccine Trial Centre, Faculty ofTropical Medicine, Mahidol University, Bangkok, Thailand; Dr F. Reigel, Vice Direc-tor, Swissmedic, Biological Medicines and Laboratories, Berne, Switzerland; Dr J.Robertson, National Institute for Biological Standards and Control, Potters Bar,Herts., England; Dr L. Slamet, Deputy for Therapeutic Products, Narcotic, Psycho-tropic and Addictive Substance Control, Directorate General of Food and DrugControl, Ministry of Health, Jakarta, Indonesia; Dr A.K. Tahlan, Central DrugsLaboratory, Central Research Institute, Kasauli, India; Ms C. Chamberlin, ScientificSecretary of European Pharmacopoeia Group of Experts on Vaccines, Strasbourg,France; Dr B. Meignier, IABS c/o Director, External R & D, Aventis Pasteur SA, Marcy
l’Etoile, France; Dr B.J. Ledwith, Director, Biologics Safety Assessment, Merck
Research Laboratories, West Point, PA, USA; Dr F. Verdier, Head, Product SafetyAssessment, Aventis Pasteur, Marcy l’Etoile, France; Dr G. del Giudice, Head,Animal Models and Serology, Research Center, Chiron SpA, Siena, Italy.
FDA-CBER-2021-5683-1148942
58WHO secretariat: Dr M.P. Kieny, Director, Initiative to Vaccine Research; Dr L.
Rago, Coordinator, Quality Assurance and Safety of Medicines; Dr D. Wood,Acting Coordinator, Quality Assurance and Safety of Biologicals; Mr L. Belgharbi,Access to Technologies; Dr N. Dellepiane, Access to Technologies; Dr P. Duclos,Vaccine Assessment and Monitoring; Dr D. Kioy, Tropical Disease Research; DrI. Knezevic, Quality Assurance and Safety of Biologicals; Dr E. Uramis Diaz,Access to Technologies; Dr S. Osmanov, Initiative to Vaccine Research/HVI.
The final draft (WHO/BS/03.1969) was prepared by Dr E. Griffiths, Dr M. Gruber,
Dr D. Masset, Dr F. Verdier, Dr D. Wood and Dr I. Knezevic, following a meetingheld in Geneva, 9–10 June 2003, and taking into account comments made by theExpert Committee on Biological Standardization at its meeting in February 2003 aswell as comments made by the reviewers of the document.
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62Appendix
List of tissues to be collected in a repeated dose
toxicity study
adrenal glands
aorta
bone (femur) and articulation
bone (sternum) with bone marrow
bone marrow smears1
brain
bronchi (main-stem)
caecum
colon
duodenum
epididymides
eyes
heart
ileum
injection site(s) (a sample should be taken from the area of injection)
jejunum
kidneys and ureters
larynx
liver
lungs
lymph node (mandibular)
lymph node (mesenteric)
mammary gland
oesophagus
optic nerves
1Bone marrow smears should be prepared at the scheduled necropsy for all animals
including any moribund animals killed during the study. The smears should be fixed in
methanol and then stained by the May-Grunwald-Giemsa method.
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63ovaries and oviducts
pancreas
parathyroid glands
Peyer’s patches
pituitary gland
prostate
rectum
salivary glands (mandibular, parotid, sublingual)
sciatic nerves
seminal vesicles
skeletal muscle
skin
spinal cord (cervical, thoracic, lumbar)
spleen
stomach
testes
thymus
thyroid glands
tongue
trachea
ureters
urinary bladder
uterus (horns + cervix)
vaginaall gross lesions
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