Early effectiveness of BNT162b2 Covid-19 vaccine in preventing SARS-CoV-2 infection in healthcare personnel in six Israeli hospitals (CoVEHPI)

Mark A. Katz, Efrat Bron Harlev, Bibiana Chazan, Michal Chowers, David Greenberg, Alon Peretz, Sagi Tshori, Joseph Levy, Mili Yacobi, Avital Hirsch, Doron Amichay, Ronit Weinberger, Anat Ben Dor, Elena Keren Taraday, Dana Reznik, Chen Barazani Chayat, Dana Sagas, Haim Ben Zvi, Rita Berdinstein, Gloria RashidYonat Shemer Avni, Michal Mandelboim, Neta Zuckerman, Nir Rainy, Amichay Akriv, Noa Dagan, Eldad Kepten, Noam Barda, Ran D. Balicer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Background: Methodologically rigorous studies on Covid-19 vaccine effectiveness (VE) in preventing SARS-CoV-2 infection are critically needed to inform national and global policy on Covid-19 vaccine use. In Israel, healthcare personnel (HCP) were initially prioritized for Covid-19 vaccination, creating an ideal setting to evaluate early real-world VE in a closely monitored population. Methods: We conducted a prospective study among HCP in 6 hospitals to estimate the effectiveness of the BNT162b2 mRNA Covid-19 vaccine in preventing SARS-CoV-2 infection. Participants filled out weekly symptom questionnaires, provided weekly nasal specimens, and three serology samples – at enrollment, 30 days and 90 days. We estimated VE against PCR-confirmed SARS-CoV-2 infection using the Cox Proportional Hazards model and against a combined PCR/serology endpoint using Fisher's exact test. Results: Of the 1567 HCP enrolled between December 27, 2020 and February 15, 2021, 1250 previously uninfected participants were included in the primary analysis; 998 (79.8%) were vaccinated with their first dose prior to or at enrollment, all with Pfizer BNT162b2 mRNA vaccine. There were four PCR-positive events among vaccinated participants, and nine among unvaccinated participants. Adjusted two-dose VE against any PCR-confirmed infection was 94.5% (95% CI: 82.6%-98.2%); adjusted two-dose VE against a combined endpoint of PCR and seroconversion for a 60-day follow-up period was 94.5% (95% CI: 63.0%-99.0%). Five PCR-positive samples from study participants were sequenced; all were alpha variant. Conclusions: Our prospective VE study of HCP in Israel with rigorous weekly surveillance found very high VE for two doses of Pfizer BNT162b2 mRNA vaccine against SARS-CoV-2 infection in recently vaccinated HCP during a period of predominant alpha variant circulation. Funding: Clalit Health Services.

Original languageEnglish
Pages (from-to)512-520
Number of pages9
Issue number3
StatePublished - 24 Jan 2022


FundersFunder number
Ayelet Sherman
Clalit Research Institute
Kaplan Medical Center
Meir Medical Center
Schneider Children's Medical Center of Israel
Soroka University Medical Center
School of Public Health, University of Michigan
Ministry of Health, State of Israel


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