Relevance. Currently, the incidence of COVID-19 is growing in many countries of the world, including Russia. There are suggestions about a likely protective role against the new coronavirus infection of widely used traditional vaccines against respiratory infections (influenza, tuberculosis, pneumococcal infection). Those vaccinated with these vaccines are less likely to report deaths and severe forms of COVID-19 diseases in vulnerable populations.The aim is to determine the frequency of detection of positive markers of a new coronavirus infection in individuals with different vaccination histories.Materials and methods. We examined 313 employees of an educational institution with various vaccination histories at the age of 20–54 years from May to September 2020. The determination of SARS-CoV-2 RNA and specific IgM and IgG antibodies to the virus nucleocapsid was carried out.Results. Positive markers for SARS-CoV-2 (PCR and / or ELISA) were found in 51 (16.3%) people. All examined patients had no signs of acute respiratory viral infections. Among people with positive markers of coronavirus infection (PCR and / or ELISA), the number of people vaccinated against diphtheria, tetanus, measles and hepatitis B (HBV) was 13.7–17.6% of those examined. Among those with negative PCR results, the number of people vaccinated against these infections was higher (p ≤ 0.05) and amounted to 51.0–56.6%. Similar results were found in the determination of specific IgM and IgG.Conclusion. Positive markers of a new coronavirus infection were found much less frequently in persons who had a history of vaccination with ADS-M-toxoid, measles and hepatitis B vaccines.

Relevance. The incidence of the novel coronavirus infection is on the rise worldwide. To effectively combat COVID-19, both vaccination and control of the circulation of SARS-CoV-2 strains among the population and, especially, foreign citizens arriving in Russia from around the world are necessary. Aim. To determine the frequency of detection of SARS-CoV-2 RNA in foreign medical students vaccinated against COVID-19 with various vaccine preparations. Materials and methods. Foreign students (510 people) of a medical university aged 18-25 years, vaccinated against COVID-19, who arrived in Russia during June-August 2021, were examined. The determination of SARS-CoV-2 RNA was carried out weekly from December 2021 to January 2022 by taking smears from the oropharynx and examining them using a test-PCR systems manufactured by the Federal State Budgetary Institution of the Central Research Institute of Epidemiology of Rospotrebnadzor «AmplisensCov-Bat-FL» (registration certificate No. RZN 2014/1987 dated 07.04.2020). Results. SARS-CoV-2 RNA was detected in 41 (8.0% [95% CI 5.6÷10.4]) of 510 international students surveyed. Among those vaccinated with vector vaccines based on human adenovirus (Sputnik V, Sputnik Light, Ad26. COV2.S (Johnson&Johnson)) SARS-CoV-2 RNA was detected in 27 (7.6% [95% CI 4.8÷10.4]) a person, mainly after 4–6 months. after vaccination; vaccines based on modified mRNA (BNT162b2 (Pfizer/BioNTech), mRNA1273 (Moderna)) – 5.7% [95% CI 1.1÷10.3] people within six months after vaccination. The infectious process was asymptomatic in 39 people, in two (vaccinated with the BNT162b2 vaccine (Pfizer / BioNTech) and Sputnik Light) it had clinical manifestations of severe and moderate severity. Conclusion. Among foreign students vaccinated against COVID-19, in addition to two cases, asymptomatic carriers of SARS-CoV-2 have been identified, which may be a potential source of infection. This indicates the need for vaccination and timely revaccination of foreign and Russian students, as well as compliance with the anti-epidemic regime.