Influence of the SARS-CoV-2 Omicron (B.1.1.529) variant and booster vaccine doses on the seroprevalence of specific IgG antibodies in the staff of the Slovak Academy of Sciences

The presented seroprevalence study focused on specific antibodies to the SARS-CoV-2 virus is the second survey conducted among SAS employees. Its realization enabled monitoring of the impact of booster vaccination doses and the spread of the Omicron variant in a defined group of people. The total seropositivity of the involved SAS employees in autumn 2022 was 96.04%. In the group of vaccinated participants (1,189) the seropositivity rate was 99.5%, while among unvaccinated participants (176) it was 72.73%. By October 2022, when the study was conducted, 65.05% (888) of the participants have had a positive PCR/Ag test for SARS-CoV-2 at least once. Based on the presence of antibodies against the nucleoprotein (NCP) of SARS-CoV-2 it was proven, that 27.39% of participants (25.12% of vaccinated; 51.22% of non-vaccinated) who have never had a positive PCR/Ag test for SARS-CoV-2, overcame the COVID-19. According to self-assessment of the disease course, it was shown that a severe course occurred in 6.31% of the participants who overcame the disease without prior vaccination and in 1.44% of the participants who overcame COVID-19 after completing the baseline vaccination scheme. The most significant finding of the study is the evidence of significantly lower levels of specific antibodies after overcoming the Omicron variant of SARS-CoV-2, and thus its reduced immunogenicity compared to ancestral virus and earlier variants of concern.