Effectiveness after immunization with BNT162b2 and Gam-COVID-Vac for SARS-CoV-2 and neutralizing antibody titers in health care workers

Objectives: The aim of this study was to describe the effectiveness of the vaccines (Tozinameran and Sputnik V), administered on a convenience sample of healthcare workers, and also to describe the relationship between the levels of neutralizing antibodies (NAbs) and the type of vaccine used, as well as their association with incident cases during follow-up. Methods: The study included 262 participants, who underwent vaccination during the period from September 2021 until August 2022. For determining the levels of NAbs we used the CLIA based method, and all the samples were processed with the SNIBE Maglumi 800 analyzer. The patients were observed for one year for occurrence of incident infection. Results: The participants with prior SARS-CoV-2 positivity showed substantially higher titer of NAbs (8.86 vs. 0.94, p<0.001). The participants in the Gam-COVID-Vac group had median levels of NAbs of 1.57 (IQR 0.42-5.73), while they in the Tozinameran group showed substantially higher levels of 2.37 (IQR 0.9-6.27). The incident cases after immunization had substantially lower median values of NAbs when compared to the rest (0.48 vs. 3.97, p<0.001), and the interval between the second dose and the serological measurements were similar. Conclusions: The current study showed that the tested vaccines demonstrated vaccine effectiveness of over 50 % during the first year after the vaccination in a sample of health care workers. Although health care workers remain separate population group, when compared to the rest, the results could be extrapolated to populations with similar age and immune experience.