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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.

Data on clinical manifestations of COVID-19 in immunocompromised patients in Russia is lacking, which prompted us to conduct a study to investigate clinical manifestations, risk factors, and outcomes of SARS-CoV-2 infection in children with oncological and hematological diseases treated at the D. Rogachev NMRCPHOI (Center). In this retrospective-prospective, nonrandomized, non-interventional study we enrolled children under 18 years with cancer, hematologic malignancies, and primary immunodeficiencies (PIDs) who underwent treatment at the Center from April 2020 to October 2021. COVID-19 cases were confirmed by polymerase chain reaction testing and classified as asymptomatic, mild, moderate, severe and critical. The study was approved by the Independent Ethics Committee and the Scientific Council of the Center. The study included 89 patients with a median age of 9.7 years and almost equal gender distribution (the male-to-female ratio was 1.1:1). Most patients (74%) were infected in a family claster. The main underlying diseases were: hemoblastoses (43.8%), solid tumors (33.7%), PIDs (14.6%). The most common clinical symptoms were fever (29%) and respiratory symptoms (47%). In 79% of cases, patients were asymptomatic or had mild symptoms; 21% of patients had moderate and severe disease (16% and 5%, accordingly). Risk factors associated with severe COVID-19 included lymphopenia (p < 0.001) and hematopoietic stem cell transplantation (HSCT) (p = 0.002). Full recovery was documented in 84% of the patients, 16% died, however COVID-attributed mortality was 5.5%. The highest mortality was in patients with moderate/severe COVID-19 (47% vs 7%, p < 0.001), in those with progression/ relapse of the underlying disease (36.3% vs 6%, p = 0.02), in children who had received specific therapy within a year before the SARS-CoV-2 diagnosis (21% vs 0%, p = 0.02), among HSCT recipients (31.6% vs 12.1%, p = 0.02), and patients with concomitant infections (33% vs 9.2%, p < 0.01). Factors associated with poor prognosis were moderate or severe COVID-19, relapse/ progression of the underlying disease, specific treatment (HSCT in particular) within 1 year before the SARS-CoV-2 diagnosis, concomitant infections, and lymphopenia. Data obtained in this study can help physicians with management decisions at this population of patients.