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Effectiveness of BNT162b2 mRNA COVID-19 Vaccine Against Acquisitions of SARS-CoV-2 Among Health Care Workers in Long-Term Care Facilities: A Prospective Cohort Study

29 Pages Posted: 19 Jul 2021

See all articles by Khitam Muhsen

Khitam Muhsen

Tel Aviv University - Department of Epidemiology and Preventive Medicine

Nimrod Maimon

Israel Ministry of Health - "Senior Shield' Project

Ami Mizrahi

Israel Ministry of Health - "Senior Shield' Project

Omri Bodenneimer

Israel Ministry of Health - "Senior Shield' Project

Dani Cohen

Tel Aviv University - Department of Epidemiology and Preventive Medicine

Michal Maimon

Ben-Gurion University of the Negev - Faculty of Health Science

Itamar Grotto

Ben-Gurion University of the Negev - Faculty of Health Science

Ron Dagan

Ben-Gurion University of the Negev - Faculty of Health Science

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Abstract

Background: We assessed vaccine effectiveness (VE) of BNT162b2 mRNA COVID-19 vaccine against SARS-CoV-2 acquisition among health care workers (HCWs) of long-term care facilities (LTCFs).

Methods: This prospective study, in the framework of "Senior Shield" program in Israel, included routine, weekly nasopharyngeal SARS-CoV-2 RT-PCR testing from all LTCF HCWs since July 2020. All residents and 75% of HCWs were immunized between December 2020 and January 2021. The analysis was limited to HCWs adhering to routine testing. Fully vaccinated (14+ days after second dose; n=6960) and unvaccinated HCWs (n=2202) were simultaneously followed until SARS-CoV-2 acquisition, or end of follow-up, April 11, 2021. Hazard ratios (HR) for vaccination vs. no vaccination were calculated (Cox proportional hazards regression models, adjusting for socio-demographics and residential-area COVID-19 incidence). VE was calculated as [(1– HR)×100]. RT-PCR cycle threshold values (Cts) were compared between vaccinated and unvaccinated HCWs.

Findings: At >14 days post second dose, 40 vaccinated HCWs acquired SARS-CoV-2 (median follow-up, 66 days; cumulative incidence 0·6%) vs. 84 unvaccinated HCWs (median follow-up 43 days; cumulative incidence, 5·1%); HR=0·11 (95% CI 0·07, 0.17), unadjusted VE=89% (95% CI 83%, 93%). Adjusted VE beyond seven days and >14 days post second dose were similar. The median PCR Cts targeting ORF1ab gene among 20 vaccinated and 40 unvaccinated HCWs was 32·0 vs. 26·7, respectively, p=0·008.

Interpretation: VE following two doses of BNT162b2 against SARS-CoV-2 acquisition in LTCF HCWs was high. The lower viral loads among SARS-CoV-2 positive HCWs suggests further reduction in transmission.

Funding Information: The current study did not have external funding sources.

Declaration of Interests: None.

Ethics Approval Statement: The study protocol was approved by the institutional review board of the Soroka University Medical Center, Beer-Sheva, Israel.

Keywords: Effectiveness; BNT162b2 vaccine; SARS-CoV-2 infection; health care workers; prospective study; Long-term care facilities, cycle threshold

Suggested Citation

Muhsen, Khitam and Maimon, Nimrod and Mizrahi, Ami and Bodenneimer, Omri and Cohen, Dani and Maimon, Michal and Grotto, Itamar and Dagan, Ron, Effectiveness of BNT162b2 mRNA COVID-19 Vaccine Against Acquisitions of SARS-CoV-2 Among Health Care Workers in Long-Term Care Facilities: A Prospective Cohort Study. Available at SSRN: https://ssrn.com/abstract=3885633 or http://dx.doi.org/10.2139/ssrn.3885633

Khitam Muhsen (Contact Author)

Tel Aviv University - Department of Epidemiology and Preventive Medicine ( email )

Tel Aviv
Israel

Nimrod Maimon

Israel Ministry of Health - "Senior Shield' Project ( email )

Israel

Ami Mizrahi

Israel Ministry of Health - "Senior Shield' Project ( email )

Israel

Omri Bodenneimer

Israel Ministry of Health - "Senior Shield' Project ( email )

Israel

Dani Cohen

Tel Aviv University - Department of Epidemiology and Preventive Medicine ( email )

Tel Aviv
Israel

Michal Maimon

Ben-Gurion University of the Negev - Faculty of Health Science ( email )

PO Box 653
Beer Sheva, 84105
Israel

Itamar Grotto

Ben-Gurion University of the Negev - Faculty of Health Science ( email )

PO Box 653
Beer Sheva, 84105
Israel

Ron Dagan

Ben-Gurion University of the Negev - Faculty of Health Science ( email )

PO Box 653
Beer Sheva, 84105
Israel

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