Neutralization assay
Investigations of live SARS-CoV-2 viruses were performed in BSL-3 facilities. We used the following SARS-CoV-2 sublineages for neutralization assays: B.1.1.1 (Wuhan, S:D614G hCoV-19/Russia/Moscow_PMVL-1/2020), B.1.1.529 Omicron BA.1 (hCoV-19/Russia/MOW-Moscow_PMVL-O16/2021), B.1.1.529 Omicron BA.2 (hCoV-19/Russia/MOW-PMVL-ON402/2022), B.1.1.529 Omicron BA.5 (hCoV-19/Russia/SPE-RII-25357S/2022). Viruses were propagated and titrated in Vero E6 cells. Viruses were titrated by microtitration method; titers were determined by the 50% tissue culture infective dose (TCID50) method, the titer was determined by the Spearman–Kaerber method. Determination of the neutralizing antibody levels in serum samples was performed by the microneutralization test as described earlier (