Method for Quantitative Assessment of Protective Immunity against Sars-Cov-2, Its Duration and Antibody Dynamics

The level and duration of protective immunity are often analyzed qualitatively or semi-quantitatively. The same strategy is applied to the analysis of antibody dynamics. At some point in time t after exposure or immunization, the presence of immunity against the infection is inferred from the level of specific antibodies by comparing it to a reference value. This approach does not account for the stochastic nature of human disease after exposure to a pathogen. At the same time, it is not fully clear what antibody level should be considered protective. The aim of this study was to develop a mathematical model for quantitative determination of protective immunity against SARS-CoV-2 and its duration. We demonstrate that the problem of describing protective immunity in quantitative terms can be broken down into 2 interrelated problems: describing the quantitative characteristics of a pathogen's virulence (in our case, the pathogen is SARS-CoV-2) and describing the dynamics of antibody titers in a biological organism. Below, we provide solutions for these problems and identify parameters of the model which describes such dynamics. Using the proposed model, we offer a theoretical solution to the problem of protective immunity and its duration. We also note that in order to quantitatively determine the studied parameters in a homogenous population group, it is necessary to know 5 parameters of the bivariate probability density function for correlated continuous random variables: the infective dose of the pathogen and the antibody titer at which the disease develops and which are still unknown.Copyright © Extreme Medicine.All right reserved.

Epidemiological Characteristics of Community-Acquired Pneumonia during the Covid-19 Epidemic in the Russian Federation

COVID-19 belongs to the group of acute respiratory infections and it is often complicated with pneumonia. This study aimed to investigate manifestations of community-acquired pneumonia (CAP) epidemic process during the COVID-19 epidemic in the Russian Federation. We analyzed the official statistical data reporting the incidence of CAP in the Russian Federation in 2013-2020 and incidence of COVID-19 as registered in March-July 2020. The mean average annual CAP incidence rate that we calculated and the 2020 CAP incidence prediction allowed assessing the relationship between CAP and COVID-19. It is shown that the long-term dynamics of the incidence of CAP in the Russian Federation is characterized by a pronounced upward trend with an average annual growth rate of 6.4%. The share of adult population among the CAP cases is the largest;on average, it is 64.7% (95% CI [63.1;66.3]). In 2020, against the background of SARS-CoV-2 circulation, the discrepancy between the actual incidence of CAP and the predicted figures reached and exceeded 558% (in July 2020). As the COVID-19 epidemic developed, the incidence of CAP was registered to increase. There was established a direct and significant correlation between the incidence of CAP and COVID-19 (rxy = 0.932;p <0.01).Copyright © 2022 Obstetrics, Gynecology and Reproduction. All rights reserved.