Study of anti-S1-protein IgG antibody levels as potential correlates of protection against breakthrough infection with SARS-CoV-2 Omicron BA.1 and BA.2 variants

Despite considerable efforts, the scientific community has not yet succeeded to define uniform correlate of protection (CoP) against SARS-CoV-2 infections based on the level of specific (receptor-binding domain (RBD)-targeting or neutralizing) antibodies (Perry et al., 2022). Obviously, this is because of the high complexity and great interindividual variability of the immune response. Although the share of cellular immunity in the response to SARS-CoV-2 infection is considerable, it would not be appropriate to underestimate the protective function of specific antibodies. Increase in their level generally correlates with a decrease in the probability of infection as well as the probability of a more severe course of the disease (Khoury et al., 2021). Determining the quantity of specific antibodies providing CoP is, however, challenging precisely in view of the individual characteristics of the T-cell branch of the immune system. However, that does not diminish the significance of studying the protective function of antibodies generated after vaccination or infection with different variants of SARS-CoV-2 against breakthrough infections with new variants of the virus. Antibodies against the RBD domain of the S1 subunit of the Spike protein have the greatest importance in the neutralization of viral particles (Dolscheid-Pommerich et al., 2022). At the same time, the OPEN ACCESS