Effect Monitoring and Insights from Vaccination program of Healthcare Workforce from a tertiary level hospital in India against SARS-CoV-2.

Ujjainiya, R.; Tyagi, A.; Sardana, V.; Naushin, S.; Bhatheja, N.; Kumar, K.; Barman, J.; Prakash, S.; Kutum, R.; Loomba, M.; Khanna, Y.; Walecha, C.; Ahmed, R.; Yadav, A.; Bajaj, A.; Malik, G.; Qureshi, S.; Waghdhare, S.; Siddiqui, S.; Trehan, K. K.; Mani, M.; Dang, R.; Das, P.; Dougall, P.; Mahajan, M.; Buddhiraja, S.; Agrawal, A.; Dash, D.; Jha, S.; Sengupta, S.

The Oxford-Astra Zeneca COVID 19 vaccine (AZD1222 or ChAdOx1) is an important part of the global vaccine roll-out against SARS-CoV-2, and a locally manufactured version (Covishield by Serum Institute, Pune, India) is the most commonly used vaccine in India. The vaccination program started in January 2021 and here we report effectiveness of the first dose of Covishield in generating antibody response and its kinetics. We further report differences in the quantitative antibody response amongst individuals who had pre-existing antibodies to SARS CoV2 and those who did not. In a group of 135 healthcare workers administered Covishield, we measured antibodies to SARS-CoV-2 directed against the spike protein (S-antigen) using Elecsys Anti-SARS-CoV-2 S quantitative antibody detection kit (Roche Diagnostics) at days 0, 7, 14, and 28. In 44 subjects (32.5%) who had already developed antibodies to SARS-CoV-2 at day 0 (before immunization), it was observed that antibody response was significantly higher at each time point, with the maximum increase seen between days 0 and 7. In contrast the sero-negative group (n=91) started developing antibody response only after 14 days or later. Three sero-negative individuals did not develop any antibody response even at day 28 of vaccination. It is noted that median antibody response at 28 days in seronegative subjects was similar to that of seropositive subjects at baseline (day 0) and was on a rising trajectory. Our data suggests that ChAdOx1 is highly immunogenic, particularly so where previous SARS CoV2 antibody-response is established. Given the high background seropositivity in India, this may be useful in determining optimal timing of the second dose during mass immunization within the constraints of vaccine supply and administration.