Epidemiological mechanism of formation of herd immunity to the novel coronavirus infection

Abstract

Based on the average value of the basic reproduction number (R0 = 4,26) of the novel coronavirus infection, epidemiological indicators characteristic of Russia were calculated, in which 53,6 % of the population was vaccinated with at least one component of the vaccine as at February 22, 2022. The calculation allowed us to establish the following values of epidemiological parameters on the specified date: (1) the effective reproduction number is 1,98; (2) a similar indicator, but adjusted for the effectiveness of the Gam-COVID-Vac (Sputnik V) vaccine, is 2,17; (3) the herd immunity threshold is at the level of 76,5 %, while (4) the critical herd immunity threshold, also taking into account the effectiveness of the Gam-COVID-Vac vaccine, is 83,5 %. The graphical dependence of the herd immunity threshold on the basic reproduction number is given. The factors influencing the level of the basic reproduction number and the formation of herd immunity in the population are discussed.