Abstract
Real-world evidence of the vaccine effectiveness (VE) of different COVID-19 vaccines is needed in order to better shape vaccine recommendations and policies and increase vaccine acceptance, especially among vulnerable populations such as the elderly. We analyzed the early effectiveness of four COVID-19 vaccines, namely BNT162b2, BBIBP-CorV, Gam-COVID-Vac and ChAdOx1 nCoV-19 in population aged ≥60 years for symptomatic, mild and severe COVID-19, in the period January–April 2021 in Vojvodina, a northern province of Serbia. Incidence rates of SARS-CoV-2 infection were calculated using data from the provincial COVID-19 surveillance registry, and vaccination coverage data were obtained from the nationwide registry of administered COVID-19 vaccines. During the observation period, 134,535 subjects aged ≥60 years were fully vaccinated, of whom 87.7% received BBIBP-CorV, 7.1% BNT162b2 and 5.2% Gam-COVID-Vac vaccines. The estimated VE in fully vaccinated persons was 86.9% (95% CI, 86–87.7) for BBIBP-CorV, 95% (95% CI, 92.4–96.7) for Gam-COVID-Vac and 99% (95% CI, 97.8–99.5) for BNT162b2, while VE after the first dose of ChAdOx1 nCoV-19 was 88.6% (95% CI, 80.5–93.4). Estimates were similar when stratifying the analyses to severe and mild SARS-CoV-2 infections. Our analysis provides evidence of high early effectiveness of BNT162b2, BBIBP-CorV, Gam-COVID-Vac and ChAdOx1 nCoV-19 in elderly people in preventing symptomatic, severe and mild COVID-19 disease, particularly after being fully vaccinated.
Highlights
The ongoing coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has major consequences for the health of the population as well as a huge impact on healthcare systems globally [1]
To obtain the vaccination status of COVID-19 cases (type and dose(s) of vaccine and date(s) of their administration), data from the surveillance registry were linked to the nationwide registry of administered COVID-19 vaccines using the Unique Master Citizen Number, a personal digit code which is assigned to all citizens of Serbia
All vaccinated individuals received the same type of vaccine for their first and second doses and followed the recommended time schedule between doses, since only the homologous regimen of COVID-19 vaccination was applied in the early phase of the immunization campaign in Serbia
Summary
The ongoing coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has major consequences for the health of the population as well as a huge impact on healthcare systems globally [1]. In Serbia, the COVID-19 vaccination campaign started on 24 December 2020, after the Serbian Medicines Agency approved the Pfizer-BioNTech BNT162b2 (Comirnaty®) vaccine. Three more vaccines, namely Sinopharm BBIBP-CorV (Vero Cell®), Gamaleya Research Institute Gam-COVID-Vac (Sputnik V®) and Oxford-AstraZeneca ChAdOx1 nCoV-19 AZD1222 (Vaxzevria®) were approved by the same agency [3]. These vaccines have different mechanisms of action and differences in terms of logistics, which are described elsewhere, but they all demonstrated satisfactory levels of safety and efficacy in controlled trial settings [4–7]. Following the BNT162b2 vaccine, BBIBP-CorV, Gam-COVID-Vac and ChAdOx1 nCoV-19 gradually became available and were offered on a voluntary basis to all adult individuals in Serbia. The recommended administration was two doses 21 days apart for the BNT162b2, BBIBP-CorV and Gam-COVID-Vac vaccines, and 12 weeks apart for the ChAdOx1 nCoV-19 vaccine
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