Frequency of SARS-CoV-2 RNA Detection in Foreign Medical Students Vaccined against New Coronavirus Infection

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.