Sequential IgG antibody monitoring for virus­inactivated and adenovirus­vectored COVID­19 vaccine in Brazilian health care workers

ABSTRACT

Vaccination certainly is the best way to fight against the COVID­19 pandemic. In this study, the seroconversion effectiveness of two vaccines against severe acute respiratory syndrome coronavirus 2 was assessed in healthcare workers virus­inactivated CoronaVac (CV, n= 303), and adenovirus­vectored Oxford­AstraZeneca (AZ, n= 447). The immunoglobulin G (IgG) antibodies anti­spike glycoprotein and anti­nucleocapsid protein were assessed by enzyme­linked immunosorbent assay at the time before vaccination (T1), before the second dose (T2), and 30 days after the second dose (T3). Of all individuals vaccinated with AZ, 100% (n= 447) exhibited seroconversion, compared to 91% (n= 276) that were given CV vaccine. Among individuals who did not respond to the CV, only three individuals showed a significant increase in the antibody level 4 months later the booster dose. A lower seroconversion rate was observed in elders immunized with the CV vaccine probably due to the natural immune senescence, or peculiarity of this vaccine. The AZ vaccine induced a higher humoral response; however, more common side effects were also observed. Nonvaccinated convalescent individuals revealed a similar rate of anti­spike IgG to individuals that were given two doses of CV vaccine, which suggests that only a one­shot COVID­19 vaccine could produce an effective immune response in convalescents.