06 RSV Adult Melgar 508

CDC ACIP — Vaccine Advisory Committee

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RSV Vaccination in Adults:
Work Group Interpretations
Michael Melgar, MD
Amadea Britton, MD, SMAdvisory Committee on Immunization PracticesOctober 24, 2024National Center for Immunization and Respiratory Diseases
2•Summarize Work Group interpretations of:
-
-
-Current RSV vaccine safety surveillance data and the balance of estimated benefits and risks 
associated with protein subunit* RSV vaccination in adults ages 60 years and older
Coadministration of RSV vaccines with other adult vaccines
Clinical trial evidence on protein subunit RSV vaccination* in immunocompromised adults
•Policy considerations for the adult RSV vaccine programOverview
*GSK’s Arexvy  and Pfizer’s Abrysvo  are protein subunit RSV vaccines. Moderna’s mResvia  is an mRNA RSV vaccine, not a protein 
subunit vaccine. 
Work Group interpretation of updated RSV vaccine safety 
data and the balance of benefits and risks of protein subunit RSV vaccination in adults 60 years and older
4•A small number of GBS cases were observed in clinical trials within 42 days after protein subunit 
RSV vaccination (GSK Arexvy , Pfizer Abrysvo ). Due to the small number of cases, it was unclear 
whether they represented a genuine association between RSV vaccination and GBS.
•Post -licensure data from 2023 –2024 from the Vaccine Adverse Event Reporting System (VAERS)1, 
the Vaccine Safety Datalink (VSD)2, and from the partnership between the Food and Drug 
Administration (FDA) and the Centers for Medicare and Medicaid Services (CMS)3,4 suggested, but 
could not confirm, an elevated risk of GBS after protein subunit RSV vaccination.
•The current older adult RSV vaccine recommendation is intended to focus the vaccination program on older adults in whom the benefits of vaccination most clearly outweigh the potential risks (all adults aged ≥75 years, adults aged 60 –74 years at increased risk of severe RSV disease).
•To date, there have been no cases of GBS within 42 days after Moderna mResvia  vaccination in 
clinical trials; post-licensure safety surveillance for this vaccine began in June 2024 after licensure and data are not yet available.RSV vaccine safety recap as of June 2024 :
Guillain -Barré syndrome (GBS)
1. https://www.cdc.gov/acip/downloads/slides -2024- 02-28-29/05- RSV- Adults -Shimabukuro -508.pdf  
2. https://www.cdc.gov/acip/downloads/slides -2024- 06-26-28/05- RSV- Adult -Donahue -508.pdf  
3. https://www.cdc.gov/acip/downloads/slides -2024- 02-28-29/06- RSV- Adults -Lloyd --508.pdf  
4. https://www.cdc.gov/acip/downloads/slides -2024- 06-26-28/06- RSV- Adult -Lloyd -508.pdf  
5As of June 2024:
•~1.3 million protein subunit RSV vaccine doses, 
2
8 GBS cases identified through diagnostic codes
•Elevated incidence rate ratio of GBS following both GSK
 Arexvy  and Pfizer Abrysvo  vaccination, but 
estimates were not statistically significant
•Data suggested difference in attributable risk by pr
oduct2
-GSK A rexvy : 3 excess cases per 1 million doses (95% CI: -3, 10)
-Pfizer A brysvo : 16 excess cases per 1 million doses (95% CI: 3, 29)
 
•No data available regarding concomitant v
accinationsUpdate October 2024:
•~3.2 million protein subunit RSV vaccine doses, 9
5 GBS cases identified through diagnostic codes 
(24 excluded through medical record review1)
•Elevated incidence rate ratio of GBS following both v
accines; results reached statistical significance for 
GSK Arexvy , but not for Pfizer Abrysvo, which had 
fewer doses administered
•Attributable GBS risk similar for both products2
-GSK A rexvy : 7 excess cases per 1 million doses (95% CI: 2, 11)
-Pfizer A brysvo : 9 excess cases per 1 million doses (95% CI: 0, 18)
•30–50% of doses were concomitantly administered 
with another vaccine; no evidence that concomitant vaccination explains the increase in GBS rate after protein subunit RSV vaccination
1.Brighton Collaboration (BC) case definition for GBS was applied, requiring Level 1 –3  certainty: https://brightoncollaboration.org/guillain -barre -and- miller -fisher -syndromes -2/. Of the 
95 initially identified cases, 51 were confirmed through medical record review, 24 were excluded (BC Level 4 –5), and 20 did not have medical record available for review. 
2.Residual confounding is possible, and the analysis was not designed to compare risk between the two vaccines. Baseline risk o f GBS ma y impact estimated attributable risk.What have we learned about GBS risk from the FDA-CMS self -controlled 
case series analysis since June 2024?
6The Work Group has previously  reviewed examples from other licensed and 
recommended vaccines of benefit -risk considerations in practice.
• Seasonal influenza vaccine: routine annual influenza vaccination is recommended for all persons aged ≥6 
months who do not have contraindications. Adults aged ≥65 years should preferentially receive high -dose, 
recombinant, or adjuvanted influenza vaccines.1
–The data on the association between GBS and seasonal influenza vaccination are variable and 
inconsistent across influenza seasons. If there is an increased risk of GBS following influenza vaccination it is small, on the order of 1–2 additional cases per million doses of influenza vaccine 
administered. Studies also suggest that it is more likely that a person will get GBS after getting influenza disease than after influenza vaccination.
2
1. Grohskopf LA, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2023 –24 Influenza Season. 
MMWR Recomm  Rep 2023;72(No. RR -2):1 –25. http://dx.doi.org/10.15585/mmwr.rr7202a1  
2. Vellozzi  C, Iqbal S, and Broder K. Guillain- Barré Syndrome, Influenza, and Influenza Vaccination: The Epidemiologic Evidence, Clinical Infectious Diseases , Volume 58, Issue 8, 15 April 2014, Pages 1149 –
1155, https://doi.org/10.1093/cid/ciu005 .
7
–
Recombinant zoster vaccine : CDC recommends two doses of recombinant zoster vaccine (RZV, Shingrix) 2–6 
months apart for adults aged ≥50 years and for adults aged ≥19 years who are or will be 
immunocompromised, for prevention of herpes zoster (shingles) and related complications.3,4
–3–6 additional cases of GBS projected per million RZV vaccinated .5
–Risk-benefit analysis incorporated available data on risk of GBS following zoster disease and vaccination with RZV
3. Dooling KL, et al. Recommendations of the Advisory Committee on Immunization Practices for Use of Herpes Zoster Vaccines. MMW R Morb  Mortal Wkly  Rep 2018;67:103– 108. http://dx.doi.org/10.15585/mmwr.mm6703a5  
4. Anderson TC, et al. Use of Recombinant Zoster Vaccine in Immunocompromised Adults Aged ≥19 Years: Recommendations of the Advi sory Committee on Immunization Practices —  United States, 2022. MMWR Morb  Mortal 
Wkly  Rep 2022;71:80 –84. http://dx.doi.org/10.15585/mmwr.mm7103a2  
5. Janusz CB, et al. Projected risks and health benefits of vaccination against herpes zoster and related complications in US ad ults. Hum Vaccin  Immunother. 2022 Nov 30;18(5):2060668. 
https://doi.org/10.1080/21645515.2022.2060668The Work Group also reviewed examples from other licensed and recommended 
vaccines of benefit -risk considerations in practice.
8Available data suggest that risk is comparable to, and potentially greater than, that of other 
c
urrently licensed and recommended adult vaccines.
No evidence of a difference in risk between protein subunit vaccines1 (GSK, Pfizer).
The Work Group emphasized that risk of GBS associated with protein subunit RSV vaccines1 
should be considered in the context of the public health benefits of RSV vaccination.
In June 2024, ACIP reviewed results of a mathematical modeling analysis comparing the n
umbers of RSV- associated hospitalizations, intensive care unit (ICU) admissions, and deaths 
avertable per 1 million persons vaccinated vs. the numbers of potential vaccine- attributable 
GBS cases.2
This analysis has been updated to account for the most up to date information on protein s
ubunit RSV vaccine effectiveness, duration of protection, and GBS risk1.The Work Group concluded that available data support existence 
of increased risk of GBS after protein subunit RSV vaccination1
1.GSK’s A rexvy  and Pfizer’s Abrysvo  are protein subunit RSV vaccines. Moderna’s mResvia  is an mRNA RSV vaccine, NOT a protein subunit vaccine. To date, Moderna’s 
mResvia  vaccine has NOT been associated with increased risk of Guillain- Barré syndrome. Post -licensure safety surveillance for mResvia  began recently in June 2024.
2.https://www.cdc.gov/acip/downloads/slides -2024 -06-26-28/09- RSV-Adult- Hutton- 508.pdf
9Same model presented in June 2024, with the following changes:
•Updated attributable risk estimates for GBS as presented earlier this morning
•Updated vaccine effectiveness (VE) assumptions
-Protein subunit RSV vaccination assumed to confer 36 months of protection 
(
increased from 24 months)
-Inclusion of preliminary first- s eason VE estimates against RSV-associated 
hospitalization from a retrospective cohort study in Medicare beneficiaries aged ≥65 years
1 in the meta -analyses of first- season VE against hospitalization1–4
•Base case evaluates protein subunit RSV vaccination generally, rather than 
th
e GSK and Pfizer vaccines individuallyBenefits and risks of protein subunit RSV vaccination 
(GSK Arexvy , Pfizer Abrysvo ): methods updates
1. Unpublished results from analysis conducted by the Food and Drug Administration (FDA), Center for Biologics Evaluation and Re se arch (CBER), Office of Biostatistics and Pharmacovigilance (OBPV) in partnership with the Centers 
for Medicare and Medicaid Services (CMS). Personal communication with CDC.
2. Surie D, Self WH, Zhu Y, et al. Investigating Respiratory Viruses in the Acutely Ill (IVY) Network. RSV Vaccine Effectiveness  Ag ainst Hospitalization Among US Adults 60 Years and Older. JAMA. 2024 Oct 1;332(13):1105- 1107. 
https://pubmed.ncbi.nlm.nih.gov/39230920/  
3. Payne AB, Watts JA, Mitchell PK, et al. Respiratory syncytial virus (RSV) vaccine effectiveness against RSV- as sociated hospitalisations and emergency department encounters among adults aged 60 years and older in the USA, 
October, 2023, to March, 2024: a test -negative design analysis. The Lancet. 2024;404(10462):1547-1559. https://doi.org/10.1016/S0140- 6736(24)01738-0  
4. Unpublished results from the Veterans Health Administration presented in June 2024: https://www.cdc.gov/acip/downloads/slides -2024- 06-26-28/07-RSV- Adult -Surie -508.pdf  
10Per 1 Million Persons Vaccinated with Protein Subunit RSV Vaccine :
1.Range of outcomes avertable was calculated using published 95% confidence intervals (outpatient only) and adjusted 95% confid en ce interval of RSV -associated incidence of the outcome observed in RSV -NET
2.FDA self - controlled case series analysis, among CMS Medicare beneficiaries ≥65 years with Parts A, B, and D coverage who did not  have a GBS claim in the 365 days before vaccination. Analysis based on 
diagnoses of GBS in inpatient claims data in risk interval (1 –42 days after RSV vaccination) compared to control interval (43 –90 days after RSV vaccination). GBS cases identified using ICD -10 diagnosis of GBS in 
primary position of inpatient claims coding with chart verification requiring Brighton Collaboration Level 1 –3 certainty. Estima tes adjusted for outcome-dependent observation time, seasonality, and (when 
chart review could not be performed) the positive predictive value of diagnostic codes in identifying chart -confirmed GBS cases.  Analysis includes patients with RSV vaccinations only through January 28, 2024 
to allow for 90-day post -vaccination observation and 90% or greater claims data completeness. Claims data through July 13, 2024. 
3.Although CMS data were limited to Medicare beneficiaries aged ≥65 years, results are extrapolated here to include adults aged 60 -64 years.
4.Credible range spans the lowest lower bound and highest upper bound of attributable risk estimates for the GSK and Pfizer RSV  v accines.Estimated RSV -Associated Outcomes1 Preventable over 3 RSV Seasons  vs. attributable risk of GBS 
estimated from self-controlled case series analysis through FDA -CMS partnership, 42-day risk interval2
0–184 attributable  cases of GBS790 830 5,600 
0 1000 2000 3000 4000 5000 6000 7000 8000 9000320 850 3,700 
0 1000 2000 3000 4000 5000 6000 7000 8000 9000Adults Aged 60–74 Years3 at Increased 
Risk of Severe RSV Disease
(1,700–6,900)
(390–1,580)
(120 –610)Hospitalizations
ICU Admissions
DeathsAd ults Aged ≥75 Years, 
General Population
(3,600–8,900)
(520–1,310)
(310–1,450)
Credit: Dr. David Hutton, U. Michigan
11•No statistical signal for GBS in rapid cycle analysis to date.
•As was seen in June 20242, there is a numerical imbalance in the number of GBS cases after 
GSK Arexvy  vaccination in adults aged ≥60 years, but the number of cases is small. The 
system is currently underpowered to determine whether there is an association with GBS.
•Similarly2, after medical record review, there is a numerical imbalance in the small number 
of cases of immune thrombocytopenia (ITP) after GSK Arexvy  vaccination without another 
simultaneous vaccine in adults aged ≥60 years, but due to the small number of cases, the 
system is currently underpowered to determine whether there is an association with ITP .
•Fewer doses of Pfizer Abrysvo  were administered in VSD, and no conclusions can be drawn 
from this system regarding the safety of this vaccine at this time.The Work Group also reviewed updated safety data from the 
Vaccine Safety Datalink (VSD) on protein subunit RSV vaccines1.
1.GSK’s Arexvy  and Pfizer’s Abrysvo  are protein subunit RSV vaccines. Moderna’s mResvia  is an mRNA RSV vaccine, NOT a protein subunit vaccine. To date, Moderna’s 
mResvia  vaccine has NOT been associated with increased risk of Guillain- Barré syndrome. Post -licensure safety surveillance for mResvia  began recently in June 2024.
2.https://www.cdc.gov/acip/downloads/slides -2024 -06-26-28/05 -RSV -Adult -Donahue-508.pdf  
Work Group interpretations on 
co-administration of RSV vaccines 
with other adult vaccines
13•Co-administration of RSV vaccines and other recommended adult vaccines, in 
particular seasonal influenza and COVID- 19 vaccines, is common
•The Work Group was reassured to see these first- ever data from Pfizer 
demonstrating that co- administration of protein subunit RSV vaccine, mRNA COVID-
19 vaccine, and high- dose influenza vaccine was safe and generated a non- inferior 
humoral immune response 
•The Work Group acknowledged the findings of an inferior RSV neutralizing antibody 
response with co- administration of Moderna RSV vaccine and high- dose influenza 
vaccine, but feels clinical significance of this finding is currently unknown
•These data should also be put in context of a lack of a consistent pattern in combinations of RSV vaccine and other concomitant vaccinations that resulted in inferior immune responsesWork Group interpretations of new co -administration 
data
14GSK RSV vaccine Pfizer RSV vaccine Moderna RSV vaccine 
Standard dose 
influenza vaccineCoadministration non
-inferior No data available Coadministration non- inferior
Adjuvanted 
influenza vaccineCoadministration non- inferiority 
criteria not met
•RSV titers: non -inferior
•Influenza titers: H3N2 HAI1titers 
inferior w/ coadministrationCoadministration non-
inferiorNo data available
High -dose influenza 
vaccineCoadministration non- inferior Coadministration non-
inferior2Coadministration non- inferiority 
criteria not met•RSV titers: RSV -A and B 
neutralizing antibody titers 
inferior w/ coadministration 
•Influenza titers: non -inferior
mRNA COVID -19 
vaccineNo data availableCoadministration non-
inferiorCoadministration non- inferiorSummary of RSV coadministration data with influenza and/or COVID -19 mRNA vaccines in 
which non -inferiority of humoral immune response was assessed in older adults
1. HAI: hemagglutination inhibition. Humoral immune response against influenza A/Darwin H3N2 was also assessed post -ho c via microne utralization, which 
resulted in a geometric mean titer (GMT) ratio similar to the HAI GMT ratio, with a slightly narrower confidence interval: 1. 23 (95% CI: 1.06 –1.42). Non -inferiority 
criteria were not specified for post -hoc analyses. Prespecified non -inferiority criteria for the HAI GMT ratio required that the  95% CI upper bound was <1.50. 
2. When given as 3 -wa y coadministration (high -dose influenza vaccine + COVID -19 vaccine + Pfizer RSV vaccine)
15•The Work Group notes our limited understanding of clinical significance of 
decreased antibody titers with RSV vaccine co -administration. 
•Given the considerable benefits of co -administration and the evidence of 
safety of co -administration, the Work Group continues to feel co -
administration is acceptable.1 
•In addition, the Work Group looks forward to learning more about Moderna’s analysis on immunologic correlates of protection for RSV as peer -
reviewed methods become available.Work Group interpretations of new co -administration 
data (continued)
1.This language is different from CDC’s General Best Practices Guidelines for Immunization, which states that with limited exce ption, 
routine administration of all age -appropriate doses of vaccines simultaneously is recommended for persons for whom no specific 
contraindications exist at the time of the visit.
Kroger A, Bahta  L, Long S, Sanchez P . General Best Practice Guidelines for Immunization. Best Practices Guidance of the Advisory Committee on  
Immunization Practices (ACIP). https://www.cdc.gov/vaccines/hcp/acip -recs/general -recs/index.html . Updated July 22, 2024; accessed October 22, 2024
Work Group interpretations on use of RSV 
vaccines in adults with immune compromise
17•During today’s meeting, GSK and Pfizer presented clinical trial data on use of 
t
heir RSV vaccines in adults aged ≥18 years with immune compromise. 
•These are the first clinical trial results in these populations at high risk of se
vere RSV disease.
•Notably, these trials studied the safety of and the immune response to RSV 
v
accination, but did not estimate efficacy against clinical endpoints. First RSV vaccine trials in immunocompromised 
persons
18What did we learn from these clinical trials?
GSK Arexvy
•Trial included adults aged ≥18 years with renal or lung 
t
ransplant
•One month after a single dose of A rexvy , these 
participants had lower RSV neutralizing antibody titers, compared with immunocompetent adults aged ≥50 years
•After a second dose of A
 rexvy  one month after the 
first, RSV neutralizing antibody titers increased and were similar to those in immunocompetent adults aged ≥50 years at 2 months post -vaccination
•Measures of cellular immunity after Arexvy  
v
accination were similar between 
immunocompromised participants and immunocompetent participants
•No specific safety concerns were identified in either clinical trial, though one participant in each trial experienced r
enal transplant rejection after RSV vaccination (judged by investigator to be unrelated to vaccination)
19What did we learn from these clinical trials?
GSK Arexvy
•Trial included adults aged ≥18 years with renal or lung 
t
ransplant 
•One month after a single dose of A rexvy , these 
participants had lower RSV neutralizing antibody titers, compared with immunocompetent adults aged ≥50 years
•After a second dose of A
 rexvy  one month after the 
first, RSV neutralizing antibody titers increased and were similar to those in immunocompetent adults aged ≥50 years at 2 months post -vaccination
•Measures of cellular immunity after Arexvy  
v
accination were similar between 
immunocompromised participants and immunocompetent participantsPfizer Abrysvo
•Trial included adults aged ≥18 years with autoimmune d
isorders on immunomodulator therapy, solid organ 
transplant, end- stage renal disease on dialysis, or non-
small cell lung cancer on therapy
•One month after a single dose of Ab rysvo , these 
participants had similar RSV neutralizing antibody titers, compared with immunocompetent adults aged ≥60 years from Pfizer’s main phase 3 trial
•The neutralizing antibody response in participants w
ith autoimmune disorders on immunomodulator 
therapy and solid organ transplant appeared lower than in adults with end- stage renal disease
•A second dose of Ab
 rysvo  one month after the first did 
not appreciably increase neutralizing antibody titers 
•No specific safety concerns were identified in either clinical trial, though one participant in each trial experienced r
enal transplant rejection after RSV vaccination (judged by investigator to be unrelated to vaccination)
20•The Work Group was encouraged to see clinical trial data in this population 
but would have preferred to see data among adults with the most severe 
forms of immune compromise, who are at highest risk of severe RSV disease 
(e.g., hematopoietic stem cell transplant, recent lung transplant).
•The Work Group also felt that Pfizer’s inclusion of adults with end -stage 
renal disease on dialysis used too broad a definition of immune compromise.
•The Work Group expressed uncertainty in whether neutralizing antibody 
titers will correspond to similar clinical efficacy observed in 
immunocompetent older adults.
•Absent clinical efficacy data, the Work Group expressed uncertainty in whether 2 doses of GSK’s Arexvy  would be required to result in adequate 
protection against severe RSV disease in solid organ transplant recipients.Work Group interpretations 
Policy considerations
22•Adults aged ≥75 years should receive a single dose of RSV vaccine
•Adults aged 60– 74 years who are at increased risk of severe RSV disease 
should receive a single dose of RSV vaccine
•While uncertainty remains regarding the magnitude of GBS risk associated 
with protein subunit RSV vaccination*, the Work Group believes that the 
benefits of RSV vaccination outweigh risks among the populations for whom 
RSV vaccination is currently recommended.The Work Group affirms that the current older adult 
RSV vaccine recommendations are appropriate.
*GSK’s Arexvy  and Pfizer’s Abrysvo  are protein subunit RSV vaccines. Moderna’s mResvia  is an mRNA RSV vaccine, NOT a protein subunit vaccine. To date, Moderna’s 
mResvia  vaccine has NOT been associated with increased risk of Guillain -Barré syndrome. Post -licensure safety surveillance for mResvia  began recently in June 2024.
23•The Work Group recognizes several important factors: 
-While risk of severe RSV disease increases with age, adults aged <60 years with 
certain chronic medical conditions have an elevated risk of severe RSV disease: some may have risk comparable to that in older adults 
-Adults from certain racial and ethnic groups may be at increased risk of these conditions at younger ages, compared with White adults
-Conditions that elevate the risk of severe RSV disease may differ by age group; conditions that place adults aged 60– 74 years at increased risk of severe RSV may 
not confer the same degree of absolute risk in adults aged 18– 59 years
-Developing RSV vaccine policy in adults <60 years will require careful consideration of the balance of public health benefits and risks in this populationThe Work Group continues to evaluate recommendations for the use 
of RSV vaccines in adults aged <60 years, acknowledging there are 
now two FDA-approved products for RSV prevention in this age group
24•As was discussed at the June 2024 ACIP meeting, the Work Group felt additional data 
on 
the potential risk of GBS associated with RSV vaccination were essential prior to 
considering RSV vaccine recommendations in adults aged <60 years
•Today we have seen updated results increasing certainty that protein subunit RSV v
accination* is associated with GBS risk, though uncertainty remains regarding the 
magnitude of risk 
•The Work Group will use these data to continue evaluating risks and benefits, including i
n which groups among adults younger than 60 years the estimated benefits outweigh 
the risks
*GSK’s Arexvy  and Pfizer’s Abrysvo  are protein subunit RSV vaccines. Moderna’s mResvia  is an mRNA RSV vaccine, NOT a protein subunit vaccine. To date, Moderna’s 
mResvia  vaccine has NOT been associated with increased risk of Guillain- Barré syndrome. Post -licensure safety surveillance for mResvia  began recently in June 2024.The Work Group continues to evaluate recommendations for the use 
of RSV vaccines in adults aged <60 years, acknowledging there are 
now two FDA-approved products for RSV prevention in this age group
25•Regarding immunocompromised adults, the Work Group recognizes this is a 
heterogeneous group who are not all at the same risk of severe RSV disease
•While the data presented today covered a subset of those with immune compromise, 
the Work Group does not feel they substantially increase certainty that those with the 
most severe forms of immune compromise will benefit from vaccination (e.g., hematopoietic stem cell transplant recipients)
•Therefore, the Work Group did not feel that the data presented today motivated an immediate policy expansion for this group in younger adults, particularly while the FDA-CMS analysis on GBS risk is still ongoingThe Work Group continues to evaluate recommendations for the use 
of RSV vaccines in adults aged <60 years, acknowledging there are 
now two FDA-approved products for RSV prevention in this age group
26•At least one complete season of safety surveillance data. 
-Depending on certainty of findings, additional data may be needed. 
•Immunobridging data in adults with immune compromise. 
•Data on duration of protection and immune response after re -vaccination.
-The Work Group expressed concern that to date there are no data showing re- vaccination will restore 
protection if efficacy wanes over time.
-While restoration of protection with re -vaccination is likely, efficacy in GSK’s pivotal phase III trial did not 
improve after re -vaccination at a 12 -month interval.1
-GSK immunogenicity data at 12 - and 24 -month re -vaccination intervals have shown a weaker humoral 
immune response, compared with the response after dose 1.2 Pfizer immunogenicity data at a 12 -month re -
vaccination interval has also shown a weaker humoral immune response, compared with the response after 
dose 1.3At the June 2024 ACIP meeting the Adult RSV Work Group indicated they 
would like to see the following data before moving to vote on an RSV 
vaccine recommendation for adults aged <60 years:
1.Ison MG, Papi  A, Athan  E et al. Efficacy and Safety of Respiratory Syncytial Virus (RSV) Prefusion F Protein Vaccine (RSVPreF3 OA) in Older Adults Over 2 RSV  Seasons. Clinical Infectious Diseases. Vol 78(6):1732 -1744. Jan 2024. 
2.Gerber, S. Arexvy  (Adjuvanted RSVPreF3) 2 -Year Update. Presented at the Advisory Committee on Immunization Practices meeting, Atlanta, GA; June 26, 2024. https://www.cdc.gov/acip/down loads/slides -2024 -06-26-28/03- RSV-Adult -Gerber -508.pdf.
3. Walsh EE et al. Respiratory Syncytial Virus Prefusion F Vaccination: Antibody Persistence and Revaccination, The Journal of Inf ectious Diseases, The Journal of Infectious Diseases, Vol. 230( 4) Pages e905–e916. Oct. 2024. 
https://academic.oup.com/jid/advance -article/doi/10.1093/infdis/jiae185/7644684 .
27•Final results from the FDA - CMS analysis from the first season of RSV 
vaccination in Medicare beneficiaries
-The Work Group continues to feel that depending on certainty of findings, additional 
da
ta may be needed, and will continue to evaluate other sources of safety data
•Pending certainty in safety findings, data demonstrating vaccine efficacy or 
e
ffectiveness against clinical endpoints in the most severely 
immunocompromised adults
-While the Work Group appreciates new immunogenicity data, they do not feel these 
da
ta are sufficient to support age expansion without final FDA -CMS results on GBS risk
•Immunogenicity data after revaccination with longer time intervals following 
in
itial vaccination
-Additional data on longer re -v accination intervals is expected from ongoing 
manufacturer clinical trials
 Today  the Work Group continues to feel additional data are necessary before 
moving to vote on an RSV vaccine recommendation for adults aged <60 years:
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.

29• Observation Period : August 6, 2023 to March 2, 2024  
o Restricted follow up to high -circulation periods after October 1, 2023 with RSV circulation ≥8 cases per 100k beneficiaries
• Outcome : RSV -associated hospitalization identified through International Classification of Diseases, 10th revision, Clinical Modification diagnostic codes
• Covariates : 
o Time-fixed covariates in the 365 days prior to index:  
Demographic  characteristics (e.g., age, sex, race), socioeconomic status (dual eligibility in Medicare/Medicaid, area deprivation index),  and health conditions (e.g., frailty 
score, general medical conditions, immunocompromised status).
Immunocompromised status is determined as a binary covariate based on the presence of immunocompromising diagnoses or treatment
o Time-varying covariates: Census tract -level infection rates
• Statistical Analysis : Marginal Structural Model with Time-Varying Cohorts  
o Inverse probability of treatment weighting 
o Doubly robust Poisson model with intercepts for the time intervals (weeks) Food and Drug Administration (FDA) RSV vaccine effectiveness analysis among 
Community -dwelling Medicare Fee -For-Service (FFS) beneficiaries aged 65 years and 
older without dialysis, preliminary results
Number of Eligible 
BeneficiariesMedian Age (IQR)Number of
RSV-associated
HospitalizationsPerson-Weeks 
(100,000)Median Follow -up 
Days Contributed to 
CategoryAdjusted VE against
RSV-associated Hospitalization 
(95% CI)
Unvaccinated 10,938,075 74 (70, 79) 12,569 2,220.7 126 Reference
Either Product 2,887,152 74 (70, 79) 486 401.8 101 81.8% (80.0%, 83.4%)
GSK RSV Vaccine 1,975,732 74 (70, 79) 352 273.1 100 80.0% (77.8%, 82.1%)
Pfizer RSV Vaccine 911,420 75 (70, 80) 134 128.6 104 84.9% (82.1%, 87.3%)Back up slide not shown at meeting