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.
【초록키워드】 Vaccine, COVID-19 vaccine, vaccination, serology, SARS-COV-2 infection, hospital, Prospective Study, variant, Infection, nasal, Symptom, BNT162b2, Pfizer, Seroconversion, PCR, Cox proportional hazards model, COVID-19 vaccination, Surveillance, Effectiveness, Alpha, Alpha variant, circulation, specimens, BNT162b2 mRNA COVID-19 vaccine, BNT162b2 mRNA, BNT162b2 mRNA vaccine, dose, healthcare personnel, proportional hazards model, Questionnaires, Participants, Enrollment, Endpoint, follow-up period, 95% CI, PCR-confirmed, first dose, PCR-positive, hazard, Study participants, participant, primary analysis, National, Fisher's exact test, Fisher, event, hcp, enrolled, evaluate, conducted, nine, provided, adjusted, predominant, study participant, creating, uninfected participant, 【제목키워드】 Vaccine, hospital, Effectiveness, of BNT162b2,