Humoral and T cell immune responses over time following SARS-CoV-2 vaccination

   In this study, we explored the development and durability of humoral and T cell immune responses among the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology staff members after vaccination with Sputnik V vaccine during the rapid spread of the novel coronavirus disease (COVID-19). The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. Three weeks after the first dose of Sputnik V vaccine, anti-spike antibodies were detected in 78.0% of the study subjects. Three weeks after the second dose, anti-spike antibodies were found in 98.4% of the subjects. Three months later, the percentage of the study subjects with anti-spike antibodies fell to 82.7 %. At first, the median antibody level increased from 198.0 BAU/mL (prior to the second vaccination) to 1050.0 BAU/mL (3 weeks after the second dose of the vaccine) but then decreased to 710.7 BAU/mL by 3 months after the full vaccination. Six months after the full vaccination, spike-specific antibodies were detectable in 82.5 % of the studied samples; the median antibody level dropped significantly (to 253.0 BAU/mL). The majority of the study subjects had SARS-CoV-2-specific T cells. They were detected in 71.9 %, 73.9 % and 67.4 % of the subjects at 3 weeks, 3 months and 6 months after the completion of the vaccination course, respectively. The level of S-specific T cells reached a peak at 3 weeks after the vaccination and was found to decline at later time points. Thus, 6 months after the vaccination with Sputnik V, we observed a reduction in both humoral and T cell-mediated immune responses, and this should be taken into consideration when implementing COVID-19 infection prevention and control measures among the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology staff members.