Populational analysis of the immunoglobulin G response to different COVID-19 vaccines in Brazil

Abstract

Vaccination is a strategy that confers protection against symptomatic infections and/or development of severe COVID-19. In Brazil, COVID-19 vaccination began in January 2021 and has been performed using vaccines from different manufactures including CoronaVac (Sinovac), ChAdOx1 (Oxford/AstraZeneca) and BNT162b2 (Pfizer/BioNTech). One of the main protective mechanisms triggered by vaccination involves the production of IgG antibodies reactive to the Spike antigen of SARS-CoV-2, the levels of which correlates with vaccine efficacy. Although phase III clinical studies confirmed the efficacy of the vaccines used in Brazil, there are just few studies comparing vaccine immunogenicity in a real-world scenario. This study aimed to depict the IgG response to natural infections and to vaccination using different types of vaccines at population scale in Matinhos, a city located in south of Brazil. Nucleocapsid seroconversion rates indicated that more than a quarter of the cohort has been subjected to natural infections by SARS-CoV-2 by the first trimester of 2022. Spike seroconversion rates achieved >95% by February 2022 and maintained stable as far as June 2022 confirming the effectiveness of the vaccination program. Immunogenicity concerning IgG reactive to Spike was higher using the BNT162b2 vaccine, followed by ChAdOx1 and CoronaVac. Natural infections boosted IgG levels reactive to Spike in those individuals that completed primary vaccination with ChAdOx1 and CoronaVac but not with BNT162b2. The levels of IgG reactive to Spike increased with the number of vaccine doses administered. The application of BNT162b2 as booster dose resulted in high levels of IgG reactive to Spike which were similar despite the type of the vaccine used during primary vaccination.