Herd Immunity to SARS-CoV-2 among the Population in Saint-Petersburg during the COVID-19 Epidemic
A. Yu. Popova, Е. Б. Ежлова, A. A. Melnikova, N. S. Bashketova, Роман Фридман, L. V. Lyalina, В. С. Смирнов, I.G. Chkhindzheriya, T. A. Grechaninova, K. A. Agapov, Наталья Арсентьева, N. A. Bazhenova, O. K. Batsunov, E. M. Danilova, Е. В. Зуева, D. V. Komkova, R. N. Kuznetsova, N. E. Lyubimova, A. N. Markova, I. V. Khamitova, V. I. Lomonosova, В. В. Ветров, A. M. Milichkina, Vladimir G. Dedkov, A. A. Totolyan
Abstract
The first case of COVID-19 was diagnosed in St. Petersburg on March 2, 2020; the period of increase in the incidence lasted for 10 weeks, the maximum rates were recorded in mid-May, and subsequently there was a statistically significant decrease in the incidence. Objective: to determine the level and structure of community immunity to SARS-CoV-2 among the population of St. Petersburg during the period of intensive spread of COVID-19. Materials and methods. Selection of volunteers for the study was carried out through interviewing and randomization. The exclusion criterion was active COVID-19 infection at the time of the survey. 2713 people aged 1 to 70 years and above were examined for the presence of specific antibodies to SARS-CoV-2. Antibodies were detected by enzyme immunoassay. Results and discussion . Studies have shown that in St. Petersburg, in the active phase of COVID-19 epidemic, there was a moderate seroprevalence to SARS-CoV-2, which amounted to 26 %, against the background of a high frequency (84.5 %) of asymptomatic infection in seropositive individuals who did not have a history of COVID-19 disease, positive PCR result and ARI symptoms on the day of examination. The maximum indicators of herd immunity were established in children 1–6 years old (31.1 %), 7–13 years old (37.7 %) and people over 70 years old (30.4 %). Differences in the level of seroprevalence in the age groups of 18–49 years are statistically significant. The highest level of seroprevalence was found among the unemployed (29.7 %), healthcare workers (27.1 %), education sector (26.4 %) and business sector personnel (25 %). In convalescents, COVID-19 antibodies are produced in 75 % of cases. In individuals with positive result of PCR analysis carried out earlier, antibodies are detected in 70 % of the cases. The results of the study of herd immunity to SARS-CoV-2 are essential to forecast the development of the epidemiological situation, as well as to plan measures for specific and non-specific prevention of COVID-19.