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The effectiveness of primary series CoronaVac vaccine in preventing COVID-19 illness: a prospective cohort study among health workers in Azerbaijan, May–November, 2021
  • +11
  • Mark Katz,
  • Madelyn Castro,
  • Nabil Seyidov,
  • M. Herdman,
  • Samir Mehdiyev,
  • C. McKnight,
  • Alina Guseinova,
  • Radu Cojocaru,
  • Jason Doran,
  • Barbara Mühlemann,
  • Javahir Suleymanova,
  • Richard Pebody,
  • Esther Kissling,
  • Gahraman Hagverdiyev
Mark Katz
World Health Organization Regional Office for Europe

Corresponding Author:markakatz@gmail.com

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Madelyn Castro
Epiconcept SAS
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Nabil Seyidov
Centre of Public Health and Reforms of the Ministry of Health
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M. Herdman
UKHSA
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Samir Mehdiyev
Centre of Public Health and Reforms of the Ministry of Health
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C. McKnight
World Health Organization Regional Office for Europe
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Alina Guseinova
World Health Organization Regional Office for Europe
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Radu Cojocaru
World Health Organization Regional Office for Europe
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Jason Doran
UKHSA
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Barbara Mühlemann
Charite Universitatsmedizin Berlin
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Javahir Suleymanova
World Health Organization Regional Office for Europe
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Richard Pebody
World Health Organization Regional Office for Europe
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Esther Kissling
EpiConcept
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Gahraman Hagverdiyev
Centre of Public Health and Reforms of the Ministry of Health
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Abstract

Background Healthcare workers (HCWs) have suffered considerable morbidity and mortality during the COVID-19 pandemic. Few studies have evaluated Coronavac vaccine effectiveness (VE), particularly in eastern Europe, where the vaccine has been widely used. Methods We conducted a prospective cohort study among HCWs in seven hospitals in Baku, Azerbaijan between May 17 to December 1, 2021, to evaluate primary series (two-dose) CoronaVac VE against symptomatic SARS-CoV-2 infection. Participants completed weekly symptom questionnaires, provided nasal swabs for SARS-CoV-2 RT-PCR testing when symptomatic, and provided serology samples at enrolment 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 covariate. Results We enrolled 1582 HCWs. At enrolment, 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 variant. The adjusted primary series VE against COVID-19 illness was 29% (95% CI:-51%;67%). For the delta-predominant period, adjusted primary series VE was 19% (95% CI:-81%;64%). For the entire analysis period, adjusted primary series VE was 39% (95% CI:-40%;73%) for HCW vaccinated within 14–149 days, and 19% (95%CI:-81;63) for those vaccinated ≥150 days. Conclusions During a delta-predominant period in Azerbaijan, point estimates suggest that primary series CoronaVac protected nearly 1 in 3 HCWs against COVID-19, but this finding was not statistically significant. Our findings underscore the need to consider booster doses in individuals who have received primary series CoronaVac.
15 Jan 2023Submitted to Influenza and other respiratory viruses
17 Jan 2023Submission Checks Completed
17 Jan 2023Assigned to Editor
27 Jan 2023Reviewer(s) Assigned
07 Feb 2023Review(s) Completed, Editorial Evaluation Pending
14 Feb 2023Editorial Decision: Revise Minor
16 Mar 20231st Revision Received
23 Mar 2023Submission Checks Completed
23 Mar 2023Assigned to Editor
26 Mar 2023Review(s) Completed, Editorial Evaluation Pending
27 Mar 2023Editorial Decision: Revise Minor
29 Apr 20232nd Revision Received
29 Apr 2023Submission Checks Completed
29 Apr 2023Assigned to Editor
03 May 2023Editorial Decision: Accept