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The effectiveness of primary series CoronaVac vaccine in preventing COVID-19 illness: A prospective cohort study among healthcare workers in Azerbaijan,May–November 2021 |
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| Authors: | Mark A. Katz Madelyn Yiseth Rojas Castro Nabil Seyidov M. Trent Herdman Samir Mehdiyev C. Jason McKnight Alina Guseinova Radu Cojocaru Jason Doran Barbara Mühlemann Christian Drosten Javahir Suleymanova Richard Pebody Esther Kissling Gahraman Hagverdiyev |
| Affiliation: | 1. World Health Organization Regional Office for Europe, Copenhagen, Denmark;2. Epiconcept, Paris, France Contribution: Conceptualization (equal), Data curation (equal), Formal analysis (lead), Methodology (equal), Writing - review & editing (equal);3. Public Health and Reforms Center, Ministry of Health, Baku, Azerbaijan Contribution: Conceptualization (equal), Data curation (equal), Investigation (equal), Methodology (equal), Project administration (equal), Resources (equal), Supervision (equal), Validation (equal), Writing - review & editing (equal);4. UK Field Epidemiology Training Programme, UK Health Security Agency, London, UK Contribution: Conceptualization (equal), Data curation (equal), Methodology (equal), Project administration (equal), Writing - review & editing (equal);5. Public Health and Reforms Center, Ministry of Health, Baku, Azerbaijan Contribution: Conceptualization (equal), Data curation (equal), Methodology (supporting), Project administration (supporting), Validation (supporting), Writing - review & editing (supporting);6. World Health Organization Regional Office for Europe, Copenhagen, Denmark Contribution: Conceptualization (supporting), Methodology (supporting), Project administration (supporting), Writing - review & editing (supporting);7. World Health Organization Regional Office for Europe, Copenhagen, Denmark Contribution: Conceptualization (supporting), Investigation (supporting), Methodology (supporting), Supervision (supporting), Writing - review & editing (supporting);8. UK Field Epidemiology Training Programme, UK Health Security Agency, London, UK Contribution: Data curation (supporting), Investigation (supporting), Methodology (supporting), Project administration (supporting), Writing - review & editing (supporting);9. Institute of Virology, Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt- Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany German Centre for Infection Research (DZIF), partner site Charité, Berlin, Germany Contribution: Data curation (supporting), Investigation (supporting), Methodology (supporting), Validation (supporting), Writing - original draft (supporting), Writing - review & editing (supporting);10. World Health Organization Country Office, Baku, Azerbaijan Contribution: Conceptualization (supporting), Project administration (supporting), Resources (supporting), Writing - review & editing (supporting);11. World Health Organization Regional Office for Europe, Copenhagen, Denmark Contribution: Conceptualization (equal), Funding acquisition (equal), Methodology (equal), Resources (supporting), Supervision (supporting), Writing - review & editing (supporting);12. Epiconcept, Paris, France;13. Public Health and Reforms Center, Ministry of Health, Baku, Azerbaijan Contribution: Conceptualization (equal), Funding acquisition (supporting), Investigation (equal), Methodology (supporting), Project administration (equal), Resources (equal), Supervision (supporting), Writing - review & editing (supporting) |
| Abstract: | BackgroundHealthcare workers (HCWs) have suffered considerable morbidity and mortality during the COVID-19 pandemic. Few studies have evaluated the CoronaVac vaccine effectiveness (VE), particularly in Eastern Europe, where the vaccine has been widely used.MethodsWe conducted a prospective cohort study among HCWs in seven hospitals in Baku, Azerbaijan between May 17 and November 30, 2021, to evaluate primary series (two-dose) CoronaVac VE against symptomatic SARS-CoV-2 infection. Participants completed weekly symptom questionnaires, provided nasopharyngeal swabs for SARS-CoV-2 RT-PCR testing when symptomatic, and provided serology samples at enrollment that were tested for anti-spike and anti-nucleocapsid antibodies. We estimated VE as (1 – hazard ratio)*100 using a Cox proportional hazards model with vaccination status as a time-varying exposure, adjusting for hospital and previous SARS-CoV-2 infection status.ResultsWe enrolled 1582 HCWs. At enrollment, 1040 (66%) had received two doses of CoronaVac; 421 (27%) were unvaccinated. During the study period, 72 PCR-positive SARS-CoV-2 infections occurred; 36/39 (92%) sequenced samples were classified as Delta variants. Primary series VE against COVID-19 illness was 29% (95% CI: −51%; 67%) for the entire analysis period. For the Delta-only period (July 1–November 30, 2021), primary series VE was 19% (95% CI: −81%; 64%). For the entire analysis period, primary series VE was 39% (95% CI: −40%; 73%) for HCWs vaccinated within 14–149 days and 19% (95% CI: −81%; 63%) for those vaccinated ≥150 days.ConclusionsDuring a period in Azerbaijan characterized by mostly Delta circulation, VE point estimates suggested that primary series CoronaVac protected nearly 1 in 3 HCWs against COVID-19, but 95% confidence intervals were wide, with lower bounds that crossed zero, reflecting the limited precision of our VE estimates. Our findings underscore the need to consider booster doses for individuals who have received the primary series of CoronaVac. |
| Keywords: | Azerbaijan CoronaVac COVID-19 healthcare workers vaccination vaccine effectiveness |