Dynamics of humoral immunity during natural SARS-CoV-2 infection and/or after vaccination with the ‘Sputnik V’ vaccine

Abstract

Comprehensive analysis of adaptive immune response to SARS-CoV-2 is critical for epidemiological monitoring, as well as for tracking immune response stages and vaccination strategies. Understanding the differences between immunity formed after COVID-19 infection and vaccine-induced immunity is a specific task within this problem. Moreover, the obvious task is to assess the effect of repeated antigenic stimulation on immunological defense against SARS-CoV-2. The aim of present study was a comparative analysis of humoral immunity (anti-SARS-CoV-2 IgA and IgG) developing after natural infection with SARS-CoV-2 and/or after vaccination with anti-COVID vaccine “Sputnik V”. The study involved 36 volunteers. 21 of them had COVID-19 and were vaccinated 8-10 months later (group 1). In 15 primarily vaccinated persons, previous SARS-CoV-2 infection was excluded by means of regular PCR screening and serological testing (group 2). Results: Intensity of humoral immune response to the primary natural SARS-CoV-2 infection and similar indexes of antiviral adaptive immunity after vaccination with “Sputnik V” vaccine were similar in both groups. However, both maximal values of anti-SARS-CoV-2 IgA and IgG and the rates of post-vaccination humoral immune response differed significantly between the persons who have previously had COVID-19 and those who have not previously been infected with SARS-CoV-2. We’ve got statistically significant differences between two groups of participants using Student’s t test comparing the average maximum IgA levels after vaccination (p < 0.05). For IgG levels, these differences are less pronounced. In the first group, the average maximal values of specific IgA and IgG levels after natural infection with SARS-CoV-2 and after subsequent vaccination differed by more than 2 times. The time intervals for reaching maximal antibody levels after vaccination proved to be significantly shorter in the subjects who had a story of COVID-19, than in persons who did not report a clinical COVID-19 infection. Concerning the terms of arising IgG antibody response after vaccination versus cases of COVID-19 in the first group, we obtained a statistically significant difference by the Student’s t-test (p < 0.05). Hence, the persons with a previous natural COVID-19 infection develop a faster, stronger and more durable response to the “Sputnik V” vaccine than the subjects who had no such infection in their history