Insights from a Pan India Sero-Epidemiological survey (Phenome-India Cohort) for SARS-CoV-2

Summary To understand the spread of SARS-CoV2, in August and September 2020, the Council of Scientific and Industrial Research (India), conducted a sero-survey across its constituent laboratories and centers across India. Of 10,427 volunteers, 1058 (10.14%) tested positive for SARS CoV2 anti-nucleocapsid (anti-NC) antibodies; 95% with surrogate neutralization activity. Three-fourth recalled no symptoms. Repeat serology tests at 3 (n=346) and 6 (n=35) months confirmed stability of antibody response and neutralization potential. Local sero-positivity was higher in densely populated cities and was inversely correlated with a 30 day change in regional test positivity rates (TPR). Regional seropositivity above 10% was associated with declining TPR. Personal factors associated with higher odds of sero-positivity were high-exposure work (Odds Ratio, 95% CI, p value; 2·23, 1·92–2·59, 6·5E-26), use of public transport (1·79, 1·43–2·24, 2·8E-06), not smoking (1·52, 1·16–1·99, 0·02), non-vegetarian diet (1·67, 1·41–1·99, 3·0E-08), and B blood group (1·36,1·15-1·61, 0·001). Impact Statement Widespread asymptomatic and undetected SARS-CoV2 infection affected more than a 100 million Indians by September 2020. Declining new cases thereafter may be due to persisting humoral immunity amongst sub-communities with high exposure. Funding Council of Scientific and Industrial Research, India (CSIR)