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Association Between Vaccination With BNT162b2 and Incidence of Symptomatic and Asymptomatic SARS-CoV-2 Infections Among Health Care Workers

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To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  What is the association between receipt of the Pfizer-BioNTech BNT162b2 vaccine and the incidence of symptomatic and asymptomatic SARS-CoV-2 infection among health care workers?

Findings  In this retrospective cohort study conducted in Tel Aviv, Israel, that included 6710 health care workers who underwent periodic testing for SARS-CoV-2 infection, vaccination with the BNT162b2 vaccine was associated with an adjusted incidence rate ratio of 0.03 for symptomatic infection and 0.14 for asymptomatic infection more than 7 days after the second dose. Both incidence rate ratios were statistically significant.

Meaning  Receipt of the BNT162b2 vaccine was significantly associated with lower incidence of symptomatic and asymptomatic SARS-CoV-2 infection among health care workers.

Abstract

Importance  Randomized clinical trials have provided estimates of the effectiveness of the BNT162b2 vaccine against symptomatic SARS-CoV-2 infection, but its effect on asymptomatic infections remains unclear.

Objective  To estimate the association of vaccination with the Pfizer-BioNTech BNT162b2 vaccine with symptomatic and asymptomatic SARS-CoV-2 infections among health care workers.

Design, Setting, and Participants  This was a single-center, retrospective cohort study conducted at a tertiary medical center in Tel Aviv, Israel. Data were collected on symptomatic and asymptomatic SARS-CoV-2 infections confirmed via polymerase chain reaction (PCR) tests in health care workers undergoing regular screening with nasopharyngeal swabs between December 20, 2020, and February 25, 2021. Logistic regression was used to calculate incidence rate ratios (IRRs) comparing the incidence of infection between fully vaccinated and unvaccinated participants, controlling for demographics and the number of PCR tests performed.

Exposures  Vaccination with the BNT162b2 vaccine vs unvaccinated status was ascertained from the employee health database. Full vaccination was defined as more than 7 days after receipt of the second vaccine dose.

Main Outcomes and Measures  The primary outcome was the regression-adjusted IRR for symptomatic and asymptomatic SARS-CoV-2 infection of fully vaccinated vs unvaccinated health care workers. The secondary outcomes included IRRs for partially vaccinated health care workers (days 7-28 after first dose) and for those considered as late fully vaccinated (>21 days after second dose).

Results  A total of 6710 health care workers (mean [SD] age, 44.3 [12.5] years; 4465 [66.5%] women) were followed up for a median period of 63 days; 5953 health care workers (88.7%) received at least 1 dose of the BNT162b2 vaccine, 5517 (82.2%) received 2 doses, and 757 (11.3%) were not vaccinated. Vaccination was associated with older age compared with those who were not vaccinated (mean age, 44.8 vs 40.7 years, respectively) and male sex (31.4% vs 17.7%). Symptomatic SARS-CoV-2 infection occurred in 8 fully vaccinated health care workers and 38 unvaccinated health care workers (incidence rate, 4.7 vs 149.8 per 100 000 person-days, respectively, adjusted IRR, 0.03 [95% CI, 0.01-0.06]). Asymptomatic SARS-CoV-2 infection occurred in 19 fully vaccinated health care workers and 17 unvaccinated health care workers (incidence rate, 11.3 vs 67.0 per 100 000 person-days, respectively, adjusted IRR, 0.14 [95% CI, 0.07-0.31]). The results were qualitatively unchanged by the propensity score sensitivity analysis.

Conclusions and Relevance  Among health care workers at a single center in Tel Aviv, Israel, receipt of the BNT162b2 vaccine compared with no vaccine was associated with a significantly lower incidence of symptomatic and asymptomatic SARS-CoV-2 infection more than 7 days after the second dose. Findings are limited by the observational design.

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Article Information

Corresponding Author: Ronen Ben-Ami, MD, Tel Aviv Sourasky Medical Center, Weizmann 6, Tel Aviv, Israel 6423906 (ronenba@tlvmc.gov.il).

Accepted for Publication: April 21, 2021.

Published Online: May 6, 2021. doi:10.1001/jama.2021.7152

Author Contributions: Drs Angel and Spitzer had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Angel and Spitzer contributed equally.

Concept and design: Angel, Henig, Sprecher, Padova, Ben-Ami.

Acquisition, analysis, or interpretation of data: Angel, Spitzer, Saiag, Sprecher.

Drafting of the manuscript: Angel, Spitzer, Henig, Saiag, Padova, Ben-Ami.

Critical revision of the manuscript for important intellectual content: Angel, Spitzer, Henig, Sprecher, Padova.

Statistical analysis: Angel, Spitzer, Ben-Ami.

Administrative, technical, or material support: Angel, Saiag, Sprecher, Padova.

Supervision: Sprecher, Padova, Ben-Ami.

Conflict of Interest Disclosures: Dr Angel reported receiving research grants from Pfizer outside the scope of this work. Dr Spitzer reported being partially supported by the Israeli Council for Higher Education via the Weizmann Data Science Research Center and by a research grant from Madame Olga Klein–Astrachan. Dr Ben-Ami reported receiving consulting fees from Pfizer, Gilead, and Merck Sharp & Dohme outside the scope of this work. No other disclosures were reported.

Additional Contributions: We thank Tanya Grossman, BSc, Shelly Zitrin, BA, and Tal Kozlovski, MSc (all 3 with the Tel Aviv Sourasky Medical Center), as well as Ran Abuhasira, MD (Rabin Medical Center), for their assistance in obtaining the data for the study and insightful comments on earlier versions of the manuscript. None of these contributors received compensation for their role in the study.

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