Seroprevalence of SARS-CoV-2-specific IgG antibodies in Kashmir, India, 7 months after the first reported local COVID-19 case: results of a population-based seroprevalence survey from October to November 2020

Khan, S Muhammad Salim; Qurieshi, Mariya Amin; Haq, Inaamul; Majid, Sabhiya; Ahmad, Javid; Ayub, Taha; Bhat, Ashfaq Ahmad; Fazili, Anjum Bashir; Ganai, Abdul Majeed; Jan, Yasmeen; Kaul, Rauf-ur-Rashid; Khan, Zahid Ali; Masoodi, Muneer Ahmad; Mushtaq, Beenish; Nazir, Fouzia; Nazir, Muzamil; Raja, Malik Waseem; Rasool, Mahbooba; Asma, Anjum; Ayoub, Shifana; Aziz, Munazza; Bhat, Arif Akbar; Chowdri, Iqra Nisar; Ismail, Shaista; Kawoosa, Misbah Ferooz; Khan, Mehvish Afzal; Khan, Mosin Saleem; Kousar, Rafiya; Lone, Ab Aziz; Nabi, Shahroz; Obaid, Mohammad; Qazi, Tanzeela Bashir; Sabah, Iram; Sumji, Ishtiyaq Ahmad

OBJECTIVES: We designed a population-based survey in Kashmir to estimate the seroprevalence of SARS-CoV-2-specific IgG antibodies in the general population aged 18 years and above. SETTING: The survey was conducted among 110 villages and urban wards across 10 districts in Kashmir from 17 October 2020 to 4 November 2020. PARTICIPANTS: Individuals aged 18 years and above were eligible to be included in the survey. Serum samples were tested for the presence of SARS-CoV-2-specific IgG antibodies using the Abbott SARS-CoV-2 IgG assay. PRIMARY AND SECONDARY OUTCOME MEASURES: We labelled assay results equal to or above the cut-off index value of 1.4 as positive for SARS-CoV-2-specific IgG antibodies. Seroprevalence estimates were adjusted for the sampling design and assay characteristics. RESULTS: Out of 6397 eligible individuals enumerated, 6315 (98.7%) agreed to participate. The final analysis was done on 6230 participants. Seroprevalence adjusted for the sampling design and assay characteristics was 36.7% (95% CI 34.3% to 39.2%). Seroprevalence was higher among the older population. Among seropositive individuals, 10.2% (247/2415) reported a history of COVID-19-like symptoms. Out of 474 symptomatic individuals, 233 (49.2%) reported having been tested. We estimated an infection fatality rate of 0.034%. CONCLUSIONS: During the first 7 months of the COVID-19 epidemic in Kashmir Valley, approximately 37% of individuals were infected. The reported number of COVID-19 cases was only a small fraction of the estimated number of infections. A more efficient surveillance system with strengthened reporting of COVID-19 cases and deaths is warranted.