cdc.gov/coronavirus

Work Group Summary

Sara Oliver MD, MSPH

ACIP Meeting

September 22, 2021
Booster doses of COVID-19 vaccines

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 Policy on booster doses will be coordinated with FDA for regulatory 

allowance, and ACIP for recommendations for use 

Review 

data 

FDA

Regulatory 

allowance

CDC/ACIP

Recommendations 

for use
 Safety and immunogenicity for a third dose of BNT162b2

 Immunity and SARS-CoV-2

 Vaccine effectiveness in the United States

 Modeling the potential impact of booster doses in nursing home residents

 Early safety monitoring for third doses of mRNA vaccines

Data to inform recommendations for booster doses of 

COVID-19 vaccines

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 23 individuals from the Phase 1 study boosted ~8 months after 2nd dose

 312 individuals from the Phase 3 study boosted ~7 months after 2nd dose

 1 month after the booster dose, geometric mean titers 3-fold higher than 1 

month after the 2nd dose

– When evaluating proportion with a seroresponse: 99.5% responded after the booster 

dose, compared to 98% after the 2nd dose

 Reactogenicity similar after the booster dose and after 2nd dose

Summary

Safety and immunogenicity for a 3rd dose of BNT162b2 (Pfizer-BioNTech presentation)

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 Limited number of individuals included in evaluations of safety and 

immunogenicity of a booster dose 

 Immunogenicity data are reassuring; unknowns remain: 

– Unknown impact of lower antibody levels pre-booster

– Unknown kinetics of antibodies over 1 month post-boost

– Unknown how boost in antibodies translate to clinical protection 

 Safety data is also reassuring; limited size: 

– 306 individuals included in safety population 

– Unable to determine risks of rare side effects (such as myocarditis) after booster dose

 Anticipate ability to review additional data from ongoing trial with ~10,000 

individuals in upcoming weeks/months

Work Group Interpretation 

Safety and immunogenicity for a third dose of BNT162b2 (Pfizer-BioNTech presentation)

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 Immune response generated by COVID-19 vaccines broad, includes cellular and 

humoral immune response

 Waning of antibodies likely do not represent the entire picture

– Memory B cells maintained out to 6 months after primary series 

 Immune response may be impacted by aging and variants 

 Transmission possible with infections after vaccination 

– Unknown how booster doses of COVID-19 vaccines may impact transmission 

Summary and Work Group Interpretation

Immunity and SARS-CoV-2

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 Significant declines in VE against infection in individuals ≥65 years of age for 

mRNA products in the Delta period 

 Smaller declines in VE against hospitalization in individuals ≥65 years of age, 

but more substantial than younger populations 

 Among adults <65 years of age, vaccines remain effective in preventing 

hospitalization and severe disease

 Vaccines may be less effective in preventing infection or milder symptomatic 

illness due to waning over time and predominance of the Delta variant

Summary and Work Group Interpretation

Vaccine effectiveness

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 Both increasing vaccination coverage of staff and increasing VE in residents can 

impact cases among LTCF residents

 Community levels of transmission substantially impact cases in LTCFs 

 To protect our vulnerable LTCF population: 

– Improve vaccine effectiveness in LTCF residents (which could include use of booster 

doses of COVID-19 vaccines)

– Increase vaccination coverage of LTCF staff

– Lower rates of community transmission

Summary and Work Group Interpretation

Modeling the potential impact of booster doses in nursing home residents

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Next Steps 
 Await FDA regulatory action

Next Steps

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Review 

data 

FDA

Regulatory 

allowance

CDC/ACIP

Recommendations 

for use

After FDA regulatory action, ACIP will have additional

discussions around recommendations for use
 Kathleen Dooling

 Heidi Moline

 Danielle Moulia

 Jefferson Jones

 Jennifer Collins

 Megan Wallace

 Monica Godfrey

 Julia Gargano

 Jack Gersten

 Eddie Shanley

 Stephen Hadler

 Hannah Rosenblum

 Heather Scobie

 Ian Plumb

 Amy Blain

 Neela Goswami

 Mary Chamberland

 Vaccine Task Force

 Epi Task Force

 Respiratory Viruses Branch

Acknowledgements

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Questions for ACIP

1. Is there additional data ACIP would need to review before discussions 

around COVID-19 vaccine policy? 
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.