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Clinical guidance for use of virus -like particle
chikungunya vaccine in pregnant and breastfeeding
womenNational Center for Emerging and Zoonotic Infectious Diseases
Susan Hills MBBS MTH
CDC Lead, Chikungunya Vaccines Work Group
Arboviral Diseases Branch
Division of Vector- Borne Diseases
Fort Collins, ColoradoDana Meaney- Delman, MD MPH FACOG
Principal Deputy Director and Chief Medical Officer
National Center on Birth Defects and Developmental
Disabilities
Chamblee, Georgia
Advisory Committee on Immunization Practices meeting
April 16 , 2025
Clinical guidance for use of virus -like
particle chikungunya vaccine (CHIK- VLP) in
pregnant women
•Clinical disease similar to non -pregnant individualsPresentation of chikungunya among pregnant women
•Adverse outcomes such as fetal loss, stillbirth, or preterm birth
documented but rare
-Mouse studies and examination of placentas from infected women suggest
placenta is refractory to chikungunya virus infection1,2
•Infection commonly results in adverse neonatal outcomes if pregnant
woman infected around time of delivery
-Intrapartum transmission occurs in ~30% –50% cases3–6
-Mechanism hypothesized to be maternal blood entering fetal circulation by placental barrier breaches from uterine contractions during labor Outcomes of chikungunya virus infection during
pregnancy
1. Fritel X et al, Emerg Infect Dis 2010; 2. Couderc T et al, PLoS Pathog 2008; 3. Gerardin P et al, PLoS Medicine 2008; 4. Ramful D et al, Ped Infect Dis J 2007; 5.
Torres JR et al, Int J Infect Dis 2016; 6. Senanayake MP et al, Ceylon Med J 2009.
•Severe and sometime fatal illness
-In one prospective study 53% (10 of 19 neonates) had severe disease1
•Presentations include encephalopathy, sepsis -like illness, cardiac,
dermatologic, and hemorrhagic manifestations
•Neurocognitive outcomes often poor, particularly if initial clinical
presentation with encephalopathyDisease in neonates infected via intrapartum transmission
Bin S et al, Clin Case Rep 2023
Jebain J et al, ID Cases 2020
Villamil -Gomez W et al, J Trop Ped 2015
1. Gerardin P et al, PLoS Medicine 2008
•Young infants infected via
mosquito -borne transmission also
at risk for severe disease, particularly during first few months of life
•Clinical presentations similar to infected neonates Chikungunya and young infants
Valamparampil JJ et al, Ind J Ped 2009
Gupta D et al, Ind J Ped 2015
•No data available on immunologic response to CHIK -VLP administered
to pregnant women
•General principles of maternal vaccination and experience with other
vaccines
-Transplacental transfer of antibodies confers protection with most vaccines
-Examples of benefits: Decreased hospitalization rates in infants (e.g.,
influenza, COVID -19, RSV vaccines) and decreased preterm birth risk (e.g.,
COVID -19 vaccine)CHIK -VLP vaccination during pregnancy: Immunogenicity
•Data insufficient to determine whether any safety risks from vaccination
during pregnancy as pregnancy an exclusion criteria in clinical trials
•Only one pregnant woman inadvertently vaccinated, was in 1st trimester
-Phase ll study with formulation of vaccine* different to licensed product
-History of 2 ectopic pregnancies
-Last menstrual period 11 days prior to vaccination
-Ectopic pregnancy detected 24 days after vaccination and assessed as
unrelated to vaccinationCHIK -VLP vaccination during pregnancy: Safety
*20µg dose of unadjuvanted vaccine
•DART study in rabbits
-Administered equivalent of human dose of vaccine on 5 occasions (i.e., twice
prior to mating, twice during gestation, and once during lactation)
-Postnatal survival rate within 28 days was lower for kits born to vaccinated
mothers ( 42% ; 95% CI : 32% –53%) compared with kits in control group ( 69% ;
95% CI 58% –80%)
-No adverse effects on other postnatal development parameters
•DART study in rats
-Reduced pup survival rates not observedVaccination during pregnancy: Developmental and
reproductive toxicology (DART) studies
•Travelers and laboratory workers
•Persons in U.S. territories and states with risk of chikungunya virus
transmissionGroups for whom clinical guidance will be relevant
•Protect pregnant woman from disease
•Avoid maternal infection around time of delivery to prevent
intrapartum virus transmission and severe disease in newborn
•Transplacental transfer of antibodies might also protect young infant from mosquito -borne transmission and severe diseaseObjectives of vaccinating pregnant women against
chikungunya
Pregnant women should avoid the risk for chikungunya virus infection, if
possible (e.g., by avoiding travel to an area with virus transmission particularly during an outbreak). Proposed clinical guidance for use of CHIK -VLP in
pregnant women
Pregnancy is a precaution for vaccination with CHIK -VLP based on the lack of
safety and immunogenicity data in pregnant women and potential safety
concerns from the toxicology study in rabbits.
In general, vaccination should be deferred until after delivery. However, in specific
circumstances it might be warranted. If the risk of infection is high and exposure
cannot be avoided, a health care provider should discuss with a pregnant woman
the potential risks of chikungunya virus infection and the potential benefits and
risks of vaccination so that vaccination can be considered.
CHIK -VLP should ideally be administered a minimum of 2 weeks prior to the
expected date of delivery, and preferably earlier, to allow protection around the
time of delivery. Proposed clinical guidance for use of CHIK -VLP in
pregnant women (2)
If pregnant women choose to be vaccinated, deferring vaccination until
after the 1st trimester (after 14 weeks gestation) might be preferred until
there are further data to clarify any potential concerns from the animal
toxicology data. In addition, it is estimated that 20% –25% of all
pregnancies lead to pregnancy loss, and the highest rates occur in the 1st
trimester, so avoiding vaccination in the 1st trimester would avoid any
association with an unrelated pregnancy loss.Proposed clinical guidance for use of CHIK -VLP in
pregnant women (3)
If both CHIK -VLP and CHIK -LA are available, vaccination with CHIK -VLP
would be preferred . Although there are no data, this is based on general
principles that vaccination with non- live vaccines is preferred over
vaccination with live vaccines for pregnant women. Proposed clinical guidance for use of CHIK -VLP in
pregnant women (4)
Guidance maximizing benefits while minimizing
potential risks of vaccination during pregnancy
1. Avoid risk of chikungunya virus exposure, if possible
2. In general, defer vaccination until after delivery
3. If exposure risk high, consider vaccination given risk for severe adverse
outcomes of infection particularly if intrapartum transmission occurs
4. If consider vaccination, where possible avoid 1st trimester and ideally
administer >2 weeks before delivery
5. If both CHIK -VLP and CHIK -LA available, vaccination with non- live CHIK -
VLP preferred
Clinical guidance for use of CHIK- VLP in
breastfeeding women
•Chikungunya viral ribonucleic acid (RNA) detected in breast milk on
very rare occasions1,2
-No studies have reported detection of replicating virus
•Case report describes mother with chikungunya and chikungunya virus
RNA detected in her breast milk who was breastfeeding her 3- month -
old infant1
-No symptoms or laboratory evidence of infection in infantChikungunya and breastfeeding
1. Campos GS et al, Pediatr Infect Dis J 2017; 2. De Paula Souza et al, Transl Res 2023.
•No data on any benefits or risks of breastfeeding after vaccination with
CHIK -VLP , including whether chikungunya antibodies present in breast
milk post -vaccination
•In toxicology studies in rabbits and rats, no impact of vaccination on
lactation was observedCHIK -VLP and breastfeeding
•To protect the woman from chikungunya
•Possible added benefit to reduce risk of infection for young infant by
transfer of protective antibodies through breast milkObjectives of vaccinating breastfeeding women
Breastfeeding women and their infants should avoid the risk for
chikungunya virus infection, if possible (e.g., by avoiding travel to an area
with transmission particularly during an outbreak).
Best practice guidelines1 for immunization note that non -live vaccines
pose no risk for mothers who are breastfeeding or their infants. Proposed clinical guidance for use of CHIK -VLP in
breastfeeding women*
*Breastfeeding not a contraindication or precaution for vaccination with CHIK -VLP
1. https://www.cdc.gov/breastfeeding/breastfeeding -special- circumstances/vaccinations -medications -drugs/vaccinations.html
•Haben Debessai, Division of Birth Defects and Infant Disorders
•Erin Staples, Division of Vector- Borne Diseases
•ACOG and AAP members for their review of draft clinical guidance
•Chikungunya Vaccines Work Group membersAcknowledgements
For more information, contact CDC
1-800- CDC- INFO (232 -4636)
TTY: 1 -888- 232- 6348 www.cdc.gov
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.