Prospective sero surveillance among healthcare workers vaccinated with ChAdOx1 nCoV-19 Corona vaccine in a tertiary hospital of Kerala, India

Njarekkattuvalappil, S. K.; Bhaskaran, R.; Vijaya Raj, S. R.; Jose, P.; Rafi, A. M.; Thomas, J.; Innah, S.; Raphael, L.; G, U. U.; R, P.; Valsan, C.; Kuttichira, P.

Background: India started Covid-19 vaccination from January 16, 2021 after the approval of two candidate vaccines namely Covishield TM and Covaxin TM .We report antibody responses among healthcare workers following two doses of CovishieldTM vaccination in a tertiary care setting. Methods: This prospective serosurveillance study was done among healthcare workers of JMMC&RI ,vaccinated during January to March 2021. Blood samples were drawn from 170 participants after their 1st dose and from 156 participants after their 2nd dose of COVID vaccine to measure the specific antibodies against the recombinant S1 subunit of the S protein of SARS CoV 2 Results: The median level of anti SARS CoV-2 Ig G antibody 28 days after the first dose vaccination is 3.64 S/C (IQR=5.91) and 11.6 S/C (IQR= 5.97) after 14 days of second dose vaccination. Protective levels of anti SARS CoV-2 Ig G antibodies is developed by 25 participants (14.7%) after 28 days of first dose of vaccination and by 109 participants (69.9%) after 14 days of second dose. 18-44 years age group (p=0.027) and absence of comorbidities (p=0.079) are associated with protective IgG levels. Conclusions: Rise in specific Ig G is observed after vaccination. Higher antibody response is observed with younger age group and absence of comorbidities, though statistically not significant. The influence of BMI is also not significant.