B-094 Vaccination Anti-SARS-Cov2 Scheme Effect on Humoral Responses on Brazilian Cohort

Abstract

Abstract Background Due to high spread of SARS-CoV-2, a global emergency vaccination program using diverse and new vaccines was implemented, providing protection mortality of COVID-19. In this way, populational investigation before and after vaccination is essential to understand and monitoring the effectiveness of these efforts. Methods Observational non-randomized study was performed using samples of 95 workers from healthcare institutions. They were vaccinated with two homologous doses of Sinovac, ChAdOx1 and Pfizer booster dose. Serum levels of anti-S1 IgA and IgG, anti-NCP IgG and neutralizing antibodies (Nabs) were measured immediately before (T0), two weeks after each dose (T1, T2), 21 days after T2 (T3) and two weeks after boost (T4). Tests were performed through commercial kits of EUROIMMUN. Results Results are summarized in Fig. 1. Anti-S1 IgG and IgA titles of CoronaVac samples showed a statistically significant increase after each vaccine dose (T1, T2 and T4). For ChAdOx1, statistically significant difference (SSD) was noticed between T1 and T4. Comparing anti- S1 IgG titles between both vaccines, SSD was observed between all collections, above 2500 BAU/mL on both.Anti-NCP titles increased after each CoronaVac dose, as expected since is an inactivated virus vaccine and SSD was observed from T1 to T4. NAbs at T3 and T4 showed SSD between collection times for each vaccine and between the vaccines. At T3 NAbs titles were higher for ChAdOx1 in comparison to Coronavac vaccinated. However, after the booster dose there was no difference of titles between vaccines and all participants were considered responsive. Conclusion The vaccine antibodies titles increased after each vaccine dose. Although there was difference of the diverse antibody titles between vaccines after 1st and 2nd doses, after booster dose all vaccinated were equally highly responsive. Such results reinforce the importance of the booster dose in the vaccination strategy against SARS-CoV-2.