Effectiveness of four vaccines in preventing SARS-CoV-2 infection in Almaty, Kazakhstan in 2021: retrospective population-based cohort study
Nabirova D. Horth R. Smagul M. Nukenova G. Yesmagambetova A. Singer D. Henderson A. Tsoy A.
2023Frontiers Media S.A.
Frontiers in Public Health
2023#11
Background: In February 2021 Kazakhstan began offering COVID-19 vaccines to adults. Breakthrough SARS-CoV-2 infections raised concerns about real-world vaccine effectiveness. We aimed to evaluate effectiveness of four vaccines against SARS-CoV-2 infection. Methods: We conducted a retrospective cohort analysis among adults in Almaty using aggregated vaccination data and individual-level breakthrough COVID-19 cases (≥14 days from 2nd dose) using national surveillance data. We ran time-adjusted Cox-proportional-hazards model with sensitivity analysis accounting for varying entry into vaccinated cohort to assess vaccine effectiveness for each vaccine (measured as 1-adjusted hazard ratios) using the unvaccinated population as reference (N = 565,390). We separately calculated daily cumulative hazards for COVID-19 breakthrough among vaccinated persons by age and vaccination month. Results: From February 22 to September 1, 2021, in Almaty, 747,558 (57%) adults were fully vaccinated (received 2 doses), and 108,324 COVID-19 cases (11,472 breakthrough) were registered. Vaccine effectiveness against infection was 79% [sensitivity estimates (SE): 74%–82%] for QazVac, 77% (SE: 71%–81%) for Sputnik V, 71% (SE: 69%–72%) for Hayat-Vax, and 70% (SE: 65%–72%) for CoronaVac. Among vaccinated persons, the 90-day follow-up cumulative hazard for breakthrough infection was 2.2%. Cumulative hazard was 2.9% among people aged ≥60 years versus 1.9% among persons aged 18–39 years (p < 0.001), and 1.2% for people vaccinated in February–May versus 3.3% in June–August (p < 0.001). Conclusion: Our analysis demonstrates high effectiveness of COVID-19 vaccines against infection in Almaty similar to other observational studies. Higher cumulative hazard of breakthrough among people ≥60 years of age and during variant surges warrants targeted booster vaccination campaigns. Copyright
breakthrough infection , COVID-19 , Kazakhstan , QazVac , SARS-CoV-2 , vaccine effectiveness
Text of the article Перейти на текст статьи
Division of Global Health Protection in Central Asia, United States Centers for Disease Control and Prevention, Almaty, Kazakhstan
Central Asia Field Epidemiology Training Program, Asfendiyarov Kazakh National Medical University, Almaty, Kazakhstan
Scientific and Practical Center of Sanitary-Epidemiological Examination and Monitoring, Branch of the National Center for Public Health, Almaty, Kazakhstan
Committee of Sanitary and Epidemiological Control, Ministry of Healthcare, Astana, Kazakhstan
Division of Global Health Protection, United States Centers for Disease Control and Prevention, Atlanta, GA, United States
Office of the Minister, Ministry of Healthcare, Astana, Kazakhstan
Division of Global Health Protection in Central Asia
Central Asia Field Epidemiology Training Program
Scientific and Practical Center of Sanitary-Epidemiological Examination and Monitoring
Committee of Sanitary and Epidemiological Control
Division of Global Health Protection
Office of the Minister
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026