IgG responses against SARS-CoV-2 vaccines AZD1222 and BBV-152 and breakthrough infections among health care workers in southern India

IgG antibodies elicited in response to SARS-CoV-2 are critical in determining the protection achieved through vaccination. The present longitudinal study aims to assess the immune response generated through AZD1222 & BBV-152 vaccination among health care workers (HCWs) in a selected hospital. Serum IgG levels were measured approximately at 1.5 months and 6 months after the first and second vaccination. The final assessment was done 12 months after the first vaccination to analyse the sustained antibody levels. Results showed a progressive increase in antibody titres as a function of time. 26 HCWs in all had SARS-CoV-2 breakthrough infection, but their antibody titres were not significantly higher compared to COVID-19 naive individuals. However, a comparative analysis showed considerably higher antibody titre in those who received the AZD1222 vaccine among this cohort. AZD1222 vaccination was significantly associated with seropositivity in the first and second assessments. Female HCWs showed significantly higher seropositivity, and participants above 60 years showed considerably reduced antibody titre in the first assessment. However, the final assessment showed no association with these variables, with 97.1 % of participants reporting to be seropositive. The results indicate good antibody response and potential protection against SARS CoV-2.