Antibody Response after First-dose of ChAdOx1-nCOV (Covishield) and BBV-152 (Covaxin) amongst Health Care Workers in India: Preliminary Results of Cross-sectional Coronavirus Vaccine-induced Antibody Titre (COVAT) study

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

Background: Two vaccines are currently being administered in India to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed the humoral immune response after the first dose of two vaccines ChAdOx1-nCOV (CovishieldTM) and BBV-152 (CovaxinTM) in Indian health care workers (HCW). Methods: This ongoing, Pan-India, Cross-sectional, Coronavirus Vaccine-induced Antibody Titre (COVAT) study is being conducted amongst HCW, with or without past history of SARS-CoV-2 infection. SARS-CoV-2 anti-spike binding antibody is being assessed quantitatively at four timepoints between 21 days or more after the first dose to 6 months after the second dose. Primary aim is to analyze antibody response following each dose of both vaccines and its correlation to age, sex, body mass index (BMI) and comorbidities. Here we report the preliminary results of anti-spike antibody response after the first dose. Results: Amongst the 552 HCW (325 Male, 227 Female), 456 and 96 received first dose of Covishield and Covaxin respectively. Overall, 79.3% showed seropositivity after the first dose. Responder rate and median (IQR) rise in anti-spike antibody was significantly higher in Covishield vs. Covaxin recipient (86.8 vs. 43.8%; 61.5 vs. 6 AU/ml; both p<0.001). This difference persisted in propensity-matched (age, sex and BMI) analysis in 172 subjects. No difference was observed with age, gender and BMI. History of hypertension had lower responder rate (65.7 vs. 82.3%, p=0.001). Covishield recipient had more adverse event vs. Covaxin arm (46.7 vs. 31.2%, p=0.006). Presence of comorbidities, past SARS-CoV-2 infection and vaccine types used were independent predictors for seropositivity after the first dose, in multiple logistic regression analysis. Conclusions: While both vaccines elicited immune response, seropositivity rates to anti-spike antibody were significantly higher in Covishield recipient compared to Covaxin after the first dose. Ongoing COVAT study will further enlighten the immune response between two vaccines after the second dose.