SARS-CoV-2 IgG Seroprevalence Detected by Chemiluminescence Immunoassay Among Healthcare Personnel and Patients in a Province With a Low Incidence Rate of COVID-19 During the First Wave of COVID-19 in Thailand

Abstract

Background There is limited evidence regarding seroprevalence during the first wave of COVID-19 in Thailand. The limited capacity of molecular laboratories in distant provinces may have resulted in fewer confirmed COVID-19 cases and possible undetected ongoing transmission, as suggested by a previously published seroprevalence study. Objectives This study aimed to assess the SARS-CoV-2 IgG and IgM seroprevalence among healthcare personnel and patients in Suddhavej Hospital and cross-reactivity of SARS-CoV-2 antibody assays with infectious and autoimmune diseases. Methods We conducted a cross-sectional study to determine seroprevalence among healthcare personnel and patients in Suddhavej Hospital, a secondary care hospital in Mahasarakham Province (population of 974,534 as of 2015). A chemiluminescence assay was used to test for IgG and/or IgM SARS-CoV-2 antibodies. Results The study included 112 healthcare personnel and 78 patients with a median age of 29 years (interquartile range, 25–40 years); 35.8% were male. The study found an IgG seroprevalence of 3 of 190 (1.6%; 95% confidence interval, 0.3%–4.5%). The 3 IgG-positive cases recalled possible exposure risk to COVID-19 infection outside the province. One case had a persistent elevated IgG level after 10 months of follow-up. No cross-reactivity was found among patients with a variety of infectious or immunologic diseases. Conclusions Our study suggests that there is a low seroprevalence among high-risk exposure groups. This evidence supports that the preventive measures used during the first wave of COVID-19 were effective in preventing asymptomatic transmission in a remote province with a low COVID-19 incidence rate.