Antibody Response after Second-dose of ChAdOx1-nCOV (CovishieldTM) and BBV-152 (CovaxinTM) among Health Care Workers in India: Final Results of Cross-sectional Coronavirus Vaccine-induced Antibody Titre (COVAT) study

SINGH, A. K.; Phatak, S. R.; SINGH, R.; Bhattacharjee, K.; Singh, N. K.; Gupta, A.; Sharma, A.

Background: We assessed the humoral immune response after the completion of two doses of both ChAdOx1-nCOV (CovishieldTM) and BBV-152 (CovaxinTM) vaccines in Indian health care workers (HCW). Methods: A Pan-India, Cross-sectional, Coronavirus Vaccine-induced Antibody Titre (COVAT) study was conducted that measured SARS-CoV-2 anti-spike binding antibody quantitatively, 21 days or more after the first and second dose of two vaccines in both severe acute respiratory syndrome (SARS-CoV-2) naive and recovered HCW. Primary aim was to analyze antibody response (seropositivity rate and median [inter-quartile range, IQR] antibody titre) following each dose of both vaccines and its correlation to age, sex, blood group, body mass index (BMI) and comorbidities. Here we report the final results of anti-spike antibody response after the two completed doses. Results: Among the 515 HCW (305 Male, 210 Female), 95.0% showed seropositivity after two doses of both vaccines. Of the 425 Covishield and 90 Covaxin recipients, 98.1% and 80.0% respectively, showed seropositivity. However, both seropositivity rate and median (IQR) rise in anti-spike antibody was significantly higher in Covishield vs. Covaxin recipient (98.1 vs. 80.0%; 127.0 vs. 53 AU/mL; both p<0.001). This difference persisted in 457 SARS-CoV-2 naive cohorts and propensity-matched (age, sex and BMI) analysis of 116 cohorts. While no difference was observed in relation to sex, BMI, blood group and any comorbidities; people with age >60 years or those with type 2 diabetes had a significantly lower seropositivity rates. Both vaccine recipients had similar solicited mild to moderate adverse events and none had severe or unsolicited side effects. In SARS-CoV-2 naive cohorts, sex, presence of comorbidities, and vaccine type were independent predictors of antibody positivity rate in multiple logistic regression analysis. Conclusions: Both vaccines elicited good immune response after two doses, although seropositivity rates and median anti-spike antibody titre was significantly higher in Covishield compared to Covaxin arm.