Neutralizing Antibody Spectrum in COVID-19 Patients who Became Ill During the Circulation of Different SARS-CoV-2 Variants

SARS-CoV-2 has been actively circulating in the human population since late 2019. During this time, the virus acquired more than 140 nucleotide mutations and 20 deletions per genome from the original variant identified in Wuhan. As the virus circulates, the proportion of re-infected individuals increases, but it is unclear how well neutralizing antibodies formed by infection with early variants neutralize the new Omicron variant lines. We analyzed the neutralizing activity of 286 sera from 286 adult patients with COVID-19 in 2020-2021, during the circulation of the prototypical lines and the Delta variant of SARS-CoV-2, against strains of the original lines and the Omicron ВА.1 and ХВВ.1.9. 2. About 10% of the sera of people who overexperienced COVID-19 while the prototypical strains were circulating and about 50% of people who overexperienced it while the Delta variant was circulating contain antibodies that neutralize Omicron ХВВ.1.9 was circulating in 2023. Thus, a fraction of people, regardless of age, who became infected in 2020-2021 have an antibody spectrum capable of neutralizing current and possibly related SARS-CoV-2 variants that will emerge in the near future. However, no strong positive correlation was found between IgG levels to RBD and NAТ titers to SARS-CoV-2 (R < 0.5), which may complicate serologic diagnosis of COVID-19 and lead to inappropriate assessment of human protection and the presence of an immune layer to SARS-CoV-2 in population-based studies.