Prevalence of Igg Antibodies Against SARS-CoV-2 Among the General Population and Healthcare Workers in India, June–July 2021

Abstract

Background: India witnessed a severe second wave of COVID-19 during March and June 2021. We did the fourth nationwide serosurvey to estimate prevalence of SARS-CoV-2 antibodies in the general population aged >=6 years and health care workers (HCWs). Methods: We did a cross-sectional study between 14 June and 6 July 2021 in 700 clusters in the same 70 districts across 21 states/Union Territory. From each district, a minimum of 400 individuals aged >=6 years from general population and 100 HCWs from the district public health facilities were included. The serum samples were tested for the presence of IgG antibodies against S1-RBD and nucleocapsid protein of SARS-CoV-2 using chemiluminescence immunoassay. We estimated the weighted and test adjusted seroprevalence of IgG antibodies against S1-RBD and/or nucleocapsid protein along with 95% CI. Findings: Of the 28,975 sera tested, the weighted and test adjusted prevalence of IgG antibodies against S1-RBD and/or nucleocapsid protein among the general population aged >=6 years was 67.6% (95% CI: 66.4 – 68.7). The seroprevalence increased with age and was not different in rural and urban areas. Compared to unvaccinated adults (62.3%, 95% CI: 60.9 – 63.7), seroprevalence was significantly higher among individuals who received one (81.0%, 95% CI: 79.6 - 82.3) and two doses (89.8%, 95% CI: 88.4 - 91.1). The seroprevalence of IgG antibodies among 7,252 health care workers was 85.2% (95% CI: 83.5 - 86.7). Interpretation: Nearly one third of the population is still seronegative. It is necessary to accelerate the coverage of COVID-19 vaccination among adults and continue adherence to non-pharmaceutical interventions.Funding: Indian Council of Medical Research. Declaration of Interest: None to declare. Ethical Approval: The Institutional Human Ethics Committee of the ICMR National Institute ofEpidemiology, Chennai approved the study protocol.