Assessment of anti-SARS-CoV-2 antibodies post-Coronavac vaccination in the Amazon region of Brazil.

Abstract

Background. The race to develop a vaccine against SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) has raised questions regarding the safety of immunizers, efficacy regarding the production of neutralizing antibodies, and the longevity of the immune response, especially when related to variables such as sex and age.Objective. The present study evaluated the frequency of seropositivity for anti-SARS-CoV-2 (S1 and S2) total antibodies and anti-SARS-CoV-2 (receptor binding domain - RBD - S1) neutralizing antibodies in individuals vaccinated with the immunizing agent Coronavac (Sinovac).Method. This was a cross-sectional study involving 358 individuals divided into two groups. Group 1 consisted of 205 volunteers who were tested for anti-SARS-CoV-2 total antibodies (S1 and S2); group 2 consisted of 153 individuals tested for the presence of anti-SARS-CoV-2 neutralizing antibodies (RBD-S1).Results. Seropositivity was greater than 70% in both groups, though approximately 20% of individuals showed no antibody production. The frequency of anti-SARS-CoV-2 total antibodies (S1 and S2) displayed a significantly different distribution between the sexes but not according to age. The frequency of anti-SARS-CoV-2 (RBD-S1) neutralizing antibodies was 93% in the age group from 21 to 40 years, which was significantly lower with advancing age, to 76% (41 to 60 years), 72% (61 to 80 years) and 47% (>80 years).Conclusion. Our results reveal a high prevalence of anti-SARS-CoV-2 total antibodies (S1 and S2) and anti-SARS-CoV-2 (RBD - S1) neutralizing antibodies in individuals who received both doses of the Coronavac vaccine, suggesting a lower efficiency of the humoral immune response among those older than 60 years of age, which might be associated with senescence of the immune system.