Serological evaluation of immune effect of inactivated COVID-19 vaccine in adult population in deqing county, Huzhou city, Zhejiang Province

ABSTRACT

ObjectiveTo investigate the specific anti-SARS-CoV-2 antibody in adults and above after initial vaccination with inactivated COVID-19 vaccine, and determine the influencing factors. MethodsIn this study, residents aged 18 and above who had completed two doses of inactivated COVID-19 vaccine in Deqing County, Huzhou City, Zhejiang Province were included. Information such as gender, age, type of vaccine and vaccination time were collected, and serum specimens were sampled. Anti-SARS-CoV-2 receptor binding domain (RBD) antibody was quantitatively examined by enzyma-linked immunosorbent assay (ELISA) and influencing factors were determined. ResultsThe median concentration of anti-SARS-CoV-2 IgG antibody in the residents vaccinated with an inactivated booster vaccine was higher than that in those vaccinated with only two doses of COVID-19 vaccine or single dose (P<0.05). The median concentration of IgG antibody in males was 9.73 (4.01-23.70) RUmL-1, lower than 17.76 (7.07-49.23) RUmL-1 in females (P<0.05). The median concentration in the residents vaccinated with BBIBP-CorV (Sinopharm) was 6.53 (0.97-13.69) RUmL-1, which was lower than that in those vaccinated with CoronaVac (Sinovac) that was 17.29 (8.54-43.73) RUmL-1 (P<0.05). The median concentration in those with BBIBP-CorV was also lower than 12 (5.45-40.06) RUmL-1 in those with heterologous booster vaccine (P<0.05). The median concentration was 9.73 (3.83-23.63) RUmL-1 in the residents with an interval of more than 6 months from the second dose, which was lower than 14.66 (6.36-35.98) RUmL-1 in those with an interval of 3-6 months (P<0.05). Moreover, immune effect was better in females (X2=16.464, P<0.05), 18-45 years (X2=7.158, P<0.05), and those vaccinated with CornaVac (X2=49.637, P<0.05), while decreased in those with an interval of more than 6 months from the second dose (X2=8.447, P<0.05). ConclusionGender, age, and type of vaccine may affect the effect of immunization. The COVID-19 vaccination shows an acceptable immunogenicity in adults;however, it declines in 6 months after vaccination. It warrants strengthening the booster vaccination to maintain the immune response.