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Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study.
Lancet. 2021 10 16; 398(10309):1407-1416.Lct

Abstract

BACKGROUND

Vaccine effectiveness studies have not differentiated the effect of the delta (B.1.617.2) variant and potential waning immunity in observed reductions in effectiveness against SARS-CoV-2 infections. We aimed to evaluate overall and variant-specific effectiveness of BNT162b2 (tozinameran, Pfizer-BioNTech) against SARS-CoV-2 infections and COVID-19-related hospital admissions by time since vaccination among members of a large US health-care system.

METHODS

In this retrospective cohort study, we analysed electronic health records of individuals (≥12 years) who were members of the health-care organisation Kaiser Permanente Southern California (CA, USA), to assess BNT162b2 vaccine effectiveness against SARS-CoV-2 infections and COVID-19-related hospital admissions for up to 6 months. Participants were required to have 1 year or more previous membership of the organisation. Outcomes comprised SARS-CoV-2 PCR-positive tests and COVID-19-related hospital admissions. Effectiveness calculations were based on hazard ratios from adjusted Cox models. This study was registered with ClinicalTrials.gov, NCT04848584.

FINDINGS

Between Dec 14, 2020, and Aug 8, 2021, of 4 920 549 individuals assessed for eligibility, we included 3 436 957 (median age 45 years [IQR 29-61]; 1 799 395 [52·4%] female and 1 637 394 [47·6%] male). For fully vaccinated individuals, effectiveness against SARS-CoV-2 infections was 73% (95% CI 72-74) and against COVID-19-related hospital admissions was 90% (89-92). Effectiveness against infections declined from 88% (95% CI 86-89) during the first month after full vaccination to 47% (43-51) after 5 months. Among sequenced infections, vaccine effectiveness against infections of the delta variant was high during the first month after full vaccination (93% [95% CI 85-97]) but declined to 53% [39-65] after 4 months. Effectiveness against other (non-delta) variants the first month after full vaccination was also high at 97% (95% CI 95-99), but waned to 67% (45-80) at 4-5 months. Vaccine effectiveness against hospital admissions for infections with the delta variant for all ages was high overall (93% [95% CI 84-96]) up to 6 months.

INTERPRETATION

Our results provide support for high effectiveness of BNT162b2 against hospital admissions up until around 6 months after being fully vaccinated, even in the face of widespread dissemination of the delta variant. Reduction in vaccine effectiveness against SARS-CoV-2 infections over time is probably primarily due to waning immunity with time rather than the delta variant escaping vaccine protection.

FUNDING

Pfizer.

Authors+Show Affiliations

Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA; Department of Health Systems Science, Kaiser Permanente Bernard J Tyson School of Medicine, Pasadena, CA, USA. Electronic address: sara.y.tartof@kp.org.Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.Department of Pediatric Infectious Diseases, Southern California Permanente Medical Group, Harbor City, CA, USA.Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.Kaiser Permanente Center for Integrated Health Care Research, Honolulu, HI, USA.Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.Pfizer, Collegeville, PA, USA.

Pub Type(s)

Evaluation Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

34619098

Citation

Tartof, Sara Y., et al. "Effectiveness of mRNA BNT162b2 COVID-19 Vaccine Up to 6 Months in a Large Integrated Health System in the USA: a Retrospective Cohort Study." Lancet (London, England), vol. 398, no. 10309, 2021, pp. 1407-1416.
Tartof SY, Slezak JM, Fischer H, et al. Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study. Lancet. 2021;398(10309):1407-1416.
Tartof, S. Y., Slezak, J. M., Fischer, H., Hong, V., Ackerson, B. K., Ranasinghe, O. N., Frankland, T. B., Ogun, O. A., Zamparo, J. M., Gray, S., Valluri, S. R., Pan, K., Angulo, F. J., Jodar, L., & McLaughlin, J. M. (2021). Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study. Lancet (London, England), 398(10309), 1407-1416. https://doi.org/10.1016/S0140-6736(21)02183-8
Tartof SY, et al. Effectiveness of mRNA BNT162b2 COVID-19 Vaccine Up to 6 Months in a Large Integrated Health System in the USA: a Retrospective Cohort Study. Lancet. 2021 10 16;398(10309):1407-1416. PubMed PMID: 34619098.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study. AU - Tartof,Sara Y, AU - Slezak,Jeff M, AU - Fischer,Heidi, AU - Hong,Vennis, AU - Ackerson,Bradley K, AU - Ranasinghe,Omesh N, AU - Frankland,Timothy B, AU - Ogun,Oluwaseye A, AU - Zamparo,Joann M, AU - Gray,Sharon, AU - Valluri,Srinivas R, AU - Pan,Kaije, AU - Angulo,Frederick J, AU - Jodar,Luis, AU - McLaughlin,John M, Y1 - 2021/10/04/ PY - 2021/08/20/received PY - 2021/09/10/revised PY - 2021/09/22/accepted PY - 2021/10/8/pubmed PY - 2021/11/4/medline PY - 2021/10/7/entrez SP - 1407 EP - 1416 JF - Lancet (London, England) JO - Lancet VL - 398 IS - 10309 N2 - BACKGROUND: Vaccine effectiveness studies have not differentiated the effect of the delta (B.1.617.2) variant and potential waning immunity in observed reductions in effectiveness against SARS-CoV-2 infections. We aimed to evaluate overall and variant-specific effectiveness of BNT162b2 (tozinameran, Pfizer-BioNTech) against SARS-CoV-2 infections and COVID-19-related hospital admissions by time since vaccination among members of a large US health-care system. METHODS: In this retrospective cohort study, we analysed electronic health records of individuals (≥12 years) who were members of the health-care organisation Kaiser Permanente Southern California (CA, USA), to assess BNT162b2 vaccine effectiveness against SARS-CoV-2 infections and COVID-19-related hospital admissions for up to 6 months. Participants were required to have 1 year or more previous membership of the organisation. Outcomes comprised SARS-CoV-2 PCR-positive tests and COVID-19-related hospital admissions. Effectiveness calculations were based on hazard ratios from adjusted Cox models. This study was registered with ClinicalTrials.gov, NCT04848584. FINDINGS: Between Dec 14, 2020, and Aug 8, 2021, of 4 920 549 individuals assessed for eligibility, we included 3 436 957 (median age 45 years [IQR 29-61]; 1 799 395 [52·4%] female and 1 637 394 [47·6%] male). For fully vaccinated individuals, effectiveness against SARS-CoV-2 infections was 73% (95% CI 72-74) and against COVID-19-related hospital admissions was 90% (89-92). Effectiveness against infections declined from 88% (95% CI 86-89) during the first month after full vaccination to 47% (43-51) after 5 months. Among sequenced infections, vaccine effectiveness against infections of the delta variant was high during the first month after full vaccination (93% [95% CI 85-97]) but declined to 53% [39-65] after 4 months. Effectiveness against other (non-delta) variants the first month after full vaccination was also high at 97% (95% CI 95-99), but waned to 67% (45-80) at 4-5 months. Vaccine effectiveness against hospital admissions for infections with the delta variant for all ages was high overall (93% [95% CI 84-96]) up to 6 months. INTERPRETATION: Our results provide support for high effectiveness of BNT162b2 against hospital admissions up until around 6 months after being fully vaccinated, even in the face of widespread dissemination of the delta variant. Reduction in vaccine effectiveness against SARS-CoV-2 infections over time is probably primarily due to waning immunity with time rather than the delta variant escaping vaccine protection. FUNDING: Pfizer. SN - 1474-547X UR - https://www.unboundmedicine.com/medline/citation/34619098/full_citation L2 - https://linkinghub.elsevier.com/retrieve/pii/S0140-6736(21)02183-8 DB - PRIME DP - Unbound Medicine ER -