Early effectiveness of BNT162b2 Covid-19 vaccine in preventing SARS-CoV-2 infection in healthcare personnel in six Israeli hospitals (CoVEHPI). Issue 3 (24th January 2022)

• Record Type: Journal Article
• Authors: Katz, Mark A.; Harlev, Efrat Bron; Chazan, Bibiana; Chowers, Michal; Greenberg, David; Peretz, Alon; Tshori, Sagi; Levy, Joseph; Yacobi, Mili; Hirsch, Avital; Amichay, Doron; Weinberger, Ronit; Dor, Anat Ben; Taraday, Elena Keren; Reznik, Dana; Chayat, Chen Barazani; Sagas, Dana; Zvi, Haim Ben; Berdinstein, Rita; Rashid, Gloria; Avni, Yonat Shemer; Mandelboim, Michal; Zuckerman, Neta; Rainy, Nir; Akriv, Amichay; Dagan, Noa; Kepten, Eldad; Barda, Noam; Balicer, Ran D.
• Is Part Of: Vaccine. Volume 40:Issue 3(2022)
• Page Start: 512
• Page End: 520
• Publication Date: 2022-01-24
• Subjects: Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2021.11.092
• Languages: English
• ISSNs: 0264-410X

Abstract

Abstract: 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.