Abstract
The global community is experiencing one of the largest infectious disease outbreaks in the 21st century. In the Saratov Region, the first case of new coronavirus infection was confirmed on March 19, 2020.The maximum increase in cases was noted between May 15 and June 30, during that time the total number of infected people in the region increased from 1526 to 6444. Since July 2020, a stable incidence level of new coronavirus infection has been observed in the Saratov Region, without a steady decline.The aim of the study was to assess the status of population immunity to the SARS-CoV-2 virus among residents of Saratov and the Saratov Region under the COVID-19 epidemic.Materials and methods. In the period from June 23 to July 26, 2020, a serological study of blood samples from 3372 volunteers of different age groups was conducted. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of reagents “ELISA anti-SARS-CoV-2 IgG” produced by the State Scientific Center of Applied Microbiology and Biotechnology of the Rospotrebnadzor (Russia).Results and discussion. In general, the incidence of COVID-19 in the Saratov Region is taking place against the background of moderate seroprevalence to the SARS-CoV-2 virus, accompanied by a high incidence of non-apparent (asymptomatic) forms of the infectious process. The absence of clinical symptoms of the disease, in the context of the limited use of methods for determining the RNA of the SARS-CoV-2 virus in PCR (11 % of the region’s population) makes it difficult to assess the real spread of the virus in the population and to establish the timing of the formation of persistent herd immunity. A low rate of antibody response among individuals with a positive result of PCR analysis, as well as among volunteers who had an infection in May, June 2020, indicates a weak formation of the immune response, or the prevalence of individuals reacting mainly by activating the cellular link of the immune system in the population. The obtained results, although they need to be explained in a number of respects, can be applied to the organization of preventive measures, including vaccination, in the region.
Highlights
the first case of new coronavirus infection was confirmed on March 19
2020.The maximum increase in cases was noted between May 15
a stable incidence level of new coronavirus infection has been observed in the Saratov Region
Summary
Цель исследования – оценка состояния популяционного иммунитета к вирусу SARS-CoV-2 среди жителей Саратова и Саратовской области в период эпидемии COVID-19. В целом заболеваемость COVID-19 в Саратовской области протекает на фоне умеренной серопревалентности к вирусу SARS-CoV-2, сопровождается высокой частотой случаев инаппарантных форм течения инфекционного процесса. Отсутствие клинических симптомов заболевания в условиях ограниченного применения методов определения РНК вируса SARS-CoV-2 в ПЦР (11 % населения региона) затрудняет достоверность оценки реального распространения вируса в популяции и установления сроков формирования стойкого популяционного иммунитета. Низкий показатель антительного ответа среди лиц с позитивным результатом ПЦР-анализа, как и у добровольцев, перенесших инфекцию в мае–июне 2020 г., свидетельствует о слабом формировании иммунного ответа либо превалировании в популяции индивидуумов, реагирующих преимущественно активацией клеточного звена иммунной системы. Полученные результаты, хотя и нуждаются в объяснении по целому ряду позиций, могут применяться для организации профилактических мероприятий, включая вакцинацию, на территории региона.
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