Characteristics of the Herd Immunity to SARS-CoV-2 in Residents of the Saratov Region under COVID-19 Epidemic

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.

SARS-CoV-2 Seroprevalence Structure of the Russian Population during the COVID-19 Pandemic

“…Perhaps the publication of this English version of the work will help to fill in information gaps to some extent. Further, it is worth mentioning that a large group of authors have already published 16 articles in Russian publications under the auspices of the head of Rospotrebnadzor, Professor A. Y. Popova [ 17 , 18 , 19 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

Features of developing SARS-CoV-2 nucleocapsid protein population-based seroprevalence during the first wave of the COVID-19 epidemic in the Russian Federation

“…или приняты к печати [1,5,6,8,10,13]. Статьи по серопревалентности еще на 13 территориях готовятся к печати.…”

“…Учитывая высокую контагиозность новой коронавирусной инфекции [25], следовало ожидать заметного роста числа вторичных контактов. Всего было выявлено 154, 25 (210,5-302,5) человек, средний уровень серопревалентности у них составил 25,3 (17,8)%. Учитывая, что полученный показатель существенно превосходит среднепопуляционный, мы попытались количественно охарактеризовать контагиозность возбудителя, основываясь на двух показателях: наличии корреляционной зависимости между серопревалетностью реконвалесцентов (в принятой в тексте терминологии) и контактных лиц.…”

“…8). Средняя величина R 0 составила 5,8 (4,(3)(4)(5)(6)(7)(8)5). Это значило, что один больной или реконвалесцент COVID-19 мог заразить в среднем 56 здоровых лиц, а в зависимости от эпидемической ситуации -до 9 здоровых лиц.…”

Creation of collective immune as the main preventive measure for the spread of the new coronavirus infection (COVID-19)

“…Понятие «коллективный иммунитет» было предложено в начале ХХ в. Популяционным (коллективным) иммунитетом называется приобретенное состояние специфической защищенности популяции или ее отдельных групп, которое складывается из иммунитета индивидуумов, входящих в эту популяцию [1].…”