We determined the antibody response among CoronaVac vaccinees who were boosted with either BNT162b2 or ChAdOx1 nCoV-19. Increase in anti-S-RBD antibodies and surrogate neutralizing antibodies against the Delta variant was higher in BNT162b2 recipients than in ChAdOx1 nCoV-19 recipients. High proportions of reactogenicity were seen for both booster regimens.
BackgroundThere 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.ObjectivesThis 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.MethodsWe 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.ResultsThe 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.ConclusionsOur 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.
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