SARS-CoV-2 sero-prevalence among general population and healthcare workers in India, December 2020 - January 2021

Abstract Background Earlier serosurveys in India revealed SARS-CoV-2 seroprevalence of 0.73% during May-June and 7.1% during August-September 2020. We conducted the third serosurvey during Dec 2020 and Jan 2021, to estimate the seroprevalence of SARS-CoV-2 infection among general population and healthcare workers (HCWs) in India. Methods We conducted the serosurvey in the same 70 districts selected for the first and second serosurveys. From each district, we enrolled at least 400 individuals aged ≥ 10 years from general population and 100 HCWs from sub-district level health facilities. Sera from general population were tested for presence of IgG antibodies against nucleocapsid (N) and spike protein (S1-RBD) of SARS-CoV-2, whereas sera from HCWs were tested for anti-S1-RBD. We estimated weighted seroprevalence adjusted for assay characteristics. Results Of the 28,598 sera from general population, 4585 (16%) had IgG antibodies against N, 6647 (23.2%) against S1-RBD and 7436 (26%) against either. The weighted and assay characteristic adjusted seroprevalence against either of the antibodies was 24.1 (95%CI: 23.0%-25.3%). Among 7385 HCWs, the seroprevalence of anti-S1-RBD IgG antibodies was 25.6% (95% CI: 23.5%-27.8%). Conclusions Nearly one in four individuals aged > = 10 years from general population as well as HCWs in India were exposed to SARS-CoV-2 by December 2020.