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Six-Month Effectiveness of BNT162B2 mRNA COVID-19 Vaccine in a Large US Integrated Health System: A Retrospective Cohort Study

40 Pages Posted: 23 Aug 2021

See all articles by Sara Y. Tartof

Sara Y. Tartof

Kaiser Permanente Southern California - Department of Research & Evaluation

Jeff M. Slezak

Kaiser Permanente Southern California - Department of Research & Evaluation

Heidi Fischer

Kaiser Permanente - Southern California Kaiser Permanente Medical Group

Vennis Hong

Kaiser Permanente Southern California - Department of Research & Evaluation

Bradley K. Ackerson

Kaiser Permanente Southern California

Omesh N. Ranasinghe

Kaiser Permanente - Southern California Kaiser Permanente Medical Group

Timothy B. Frankland

Kaiser Permanente - Kaiser Permanente Center for Integrated Health Care Research

Oluwaseye A. Ogun

Kaiser Permanente Southern California - Department of Research & Evaluation

Joann M. Zamparo

Pfizer, Inc.

Sharon Gray

Pfizer, Inc.

Srinivas R. Valluri

Pfizer, Inc.

Kaijie Pan

Pfizer, Inc.

Frederick J. Angulo

Pfizer, Inc.

Luis Jodar

Pfizer, Inc. - Vaccines Medical Development & Scientific Affairs

John M. McLaughlin

Pfizer, Inc.

More...

Abstract

Background: Vaccine effectiveness (VE) studies have not differentiated the impact of Delta from potential waning immunity on recent observed reductions in effectiveness against SARS-CoV-2 infections. We evaluated overall and variant-specific effectiveness of BNT162b2 against SARS-CoV-2 infections and COVID-19-related hospitalizations by time since vaccination among members of a large US healthcare system.

Methods: In this retrospective cohort study, we analyzed electronic health records from Kaiser Permanente Southern California (KPSC) between Dec 14, 2020 – Aug 8, 2021 to assess BNT162b2 VE against SARS-CoV-2 infections and COVID-19-related hospitalization. Effectiveness calculations were based on hazards ratios from adjusted Cox models.

Findings: For fully vaccinated individuals, effectiveness against SARS-CoV-2 infections was 73% (95%CI: 72‒74) and against COVID-19-related hospitalizations was 90% (89‒92). Effectiveness against infections declined from 88% (86‒89) during the first month after full vaccination to 47% (43‒51) after ≥5 months. Among sequenced infections, VE against Delta was lower compared to VE against other variants (75% [71‒78] vs 91% [88‒92]). VE against Delta infections was high during the first month after full vaccination (93% [85‒97]) but declined to 53% [39‒65] at ≥4 months. VE against hospitalization for Delta for all ages was high overall (93%).

Interpretation: Our results confirm high effectiveness of BNT162b2 against hospitalizations through roughly six months after being fully vaccinated, even in the face of widespread dissemination of Delta. Reductions in effectiveness against SARS-CoV-2 infections over time are likely primarily due to waning rather than Delta escaping vaccine protection.

Trial Registration: NCT04848584

Funding: Pfizer Inc.

Declaration of Interest: JMZ, SG, KP, FJA, LJ, and JMM are employees of and hold stock and/or stock options in Pfizer Inc. TBF holds stock in Pfizer Inc. SYT received research support from Pfizer during the conduct of this study. All other authors report no conflicts.

Ethical Approval: The study protocol was reviewed and approved by the KPSC institutional review board, which waived requirement for informed consent (IRB#12816).

Suggested Citation

Tartof, Sara Y. and Slezak, Jeff M. and Fischer, Heidi and Hong, Vennis and Ackerson, Bradley K. and Ranasinghe, Omesh N. and Frankland, Timothy B. and Ogun, Oluwaseye A. and Zamparo, Joann M. and Gray, Sharon and Valluri, Srinivas R. and Pan, Kaijie and Angulo, Frederick J. and Jodar, Luis and McLaughlin, John M., Six-Month Effectiveness of BNT162B2 mRNA COVID-19 Vaccine in a Large US Integrated Health System: A Retrospective Cohort Study. Available at SSRN: https://ssrn.com/abstract=3909743 or http://dx.doi.org/10.2139/ssrn.3909743

Sara Y. Tartof (Contact Author)

Kaiser Permanente Southern California - Department of Research & Evaluation ( email )

Pasadena, CA
United States

Jeff M. Slezak

Kaiser Permanente Southern California - Department of Research & Evaluation ( email )

Heidi Fischer

Kaiser Permanente - Southern California Kaiser Permanente Medical Group ( email )

Mission Viejo, CA
United States

Vennis Hong

Kaiser Permanente Southern California - Department of Research & Evaluation ( email )

Mission Viejo, CA
United States

Bradley K. Ackerson

Kaiser Permanente Southern California ( email )

Mission Viejo, CA
United States

Omesh N. Ranasinghe

Kaiser Permanente - Southern California Kaiser Permanente Medical Group ( email )

Mission Viejo, CA
United States

Timothy B. Frankland

Kaiser Permanente - Kaiser Permanente Center for Integrated Health Care Research ( email )

Honolulu,, HI
United States

Oluwaseye A. Ogun

Kaiser Permanente Southern California - Department of Research & Evaluation ( email )

Mission Viejo, CA
United States

Joann M. Zamparo

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

Sharon Gray

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

Srinivas R. Valluri

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

Kaijie Pan

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

Frederick J. Angulo

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

Luis Jodar

Pfizer, Inc. - Vaccines Medical Development & Scientific Affairs

New York City, NY
United States

John M. McLaughlin

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

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