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Effectiveness of a Third Dose of BNT162b2 mRNA COVID-19 Vaccine in a Large US Health System: A Retrospective Cohort Study

35 Pages Posted: 21 Dec 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

Laura Puzniak

Pfizer, Inc.

Vennis Hong

Kaiser Permanente Southern California - Department of Research & Evaluation

Timothy B. Frankland

Kaiser Permanente - Kaiser Permanente Center for Integrated Health Care Research

Bradley K. Ackerson

Kaiser Permanente Southern California

Harpreet S. Takhar

Kaiser Permanente Southern California - Department of Research & Evaluation

Oluwaseye A. Ogun

Kaiser Permanente Southern California - Department of Research & Evaluation

Sarah Simmons

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.

Luis Jodar

Pfizer, Inc. - Vaccines Medical Development & Scientific Affairs

John M. McLaughlin

Pfizer, Inc.

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Abstract

Background: Globally, recommendations are expanding for third (booster) doses of BNT162b2. In the United States, as of November 19, 2021, boosters were recommended for all adults aged 18 years and older. We evaluated the effectiveness of a third dose of BNT162b2 among adults in a large US integrated health system.

Methods: In this retrospective cohort study, we analyzed electronic health records from Kaiser Permanente Southern California between Dec 14, 2020 and Dec 5, 2021 to assess vaccine effectiveness (VE) of two and three doses of BNT162b2 against SARS-CoV-2 infections and COVID-19-related hospital admission. VE was calculated using hazards ratios from adjusted Cox models.

Findings: After only two doses, VE against infection declined from 85% (95% CI 83–86) during the first month to 49% (46–51) seven to eight months following vaccination. Overall VE against hospitalization was 90% (95% CI 86–92) within one month and did not wane, however, effectiveness against hospitalization appeared to wane among immunocompromised individuals. Three-dose VE was 88% (95% CI 86–89) against infection and 97% (95–98) against hospitalization. Effectiveness after three doses was higher than that seen one month after receiving only two doses for both outcomes. Relative VE of three doses compared to two (with at least six months after the second dose) was 75% (95% CI 71−78) and 70% (48−83) against infections and hospital admissions, respectively.

Interpretation: These data support the benefit of broad BNT162b2 booster recommendations, as three doses confers comparable, if not better, protection against SARS-CoV-2 infections and hospital admission as was seen soon after receiving two doses.

Trial Registration: This study was registered with: NCT04848584.

Funding: Pfizer Inc.

Declaration of Interest: JMZ, SG, SRV, KP, LJ, LP, and JMM are employees of and hold stock and/or stock options in Pfizer Inc. TBF holds stock in Pfizer Inc. SYT, JMS, VH, BA, HT, TF, SRS, and OO received research support from Pfizer during the conduct of this study that was paid directly to KPSC. 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 (number 12816).

Keywords: effectiveness, waning, booster, third dose, BNT162b2, SARS-CoV-2, COVID-19, United States, cohort, delta

Suggested Citation

Tartof, Sara Y. and Slezak, Jeff M. and Puzniak, Laura and Hong, Vennis and Frankland, Timothy B. and Ackerson, Bradley K. and Takhar, Harpreet S. and Ogun, Oluwaseye A. and Simmons, Sarah and Zamparo, Joann M. and Gray, Sharon and Valluri, Srinivas R. and Pan, Kaijie and Jodar, Luis and McLaughlin, John M., Effectiveness of a Third Dose of BNT162b2 mRNA COVID-19 Vaccine in a Large US Health System: A Retrospective Cohort Study. Available at SSRN: https://ssrn.com/abstract=3989856 or http://dx.doi.org/10.2139/ssrn.3989856

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 )

Laura Puzniak

Pfizer, Inc.

La Jolla, CA
United States

Vennis Hong

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

Mission Viejo, CA
United States

Timothy B. Frankland

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

Honolulu,, HI
United States

Bradley K. Ackerson

Kaiser Permanente Southern California ( email )

Mission Viejo, CA
United States

Harpreet S. Takhar

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

Mission Viejo, CA
United States

Oluwaseye A. Ogun

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

Mission Viejo, CA
United States

Sarah Simmons

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

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

Luis Jodar

Pfizer, Inc. - Vaccines Medical Development & Scientific Affairs

John M. McLaughlin

Pfizer, Inc. ( email )

235 East 42 Street
New York, NY 10017
United States

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