Seroprevalence of Hospital Staff in Province with Zero COVID-19 cases


Tanawin Nopsopon, Krit Pongpirul, Korn Chotirosniramit, Wutichai Jakaew, Chuenkhwan Kaewwijit, Sawan Kanchana, Narin Hiransuthikul


COVID-19 seroprevalence data has been scarce, especially in less developed countries with a relatively low infection rate.


A locally developed rapid IgM/IgG test kit was used for screening hospital staff in Ranong hospital which located in a province with zero COVID-19 prevalence in Thailand from April 17 to May 17, 2020. A total of 844 participants were tested; 82 of which were tested twice with one month apart. (Thai Clinical Trials Registry: TCTR20200426002)


Overall, 0.8% of the participants (7 of 844) had positive immunoglobulin M (IgM), none had positive immunoglobulin G (IgG). Female staffs seemed to have higher IgM seropositive than male staffs (1.0% vs. 0.5%). None of the participants with a history of travel to the high-risk area or a history of close contact with PCR-confirmed COVID-19 case had developed antibodies against SARS-CoV-2. Among 844 staff, 811 had no symptom and six of them developed IgM seropositive (0.7%) while 33 had minor symptoms and only one of them developed IgM seropositive (3.0%). No association between IgM antibody against SARS-CoV-2 status and gender, history of travel to a high-risk area, history of close contact with PCR-confirmed COVID-19 case, history of close contact with suspected COVID-19 case, presence of symptoms within 14 days, or previous PCR status was found. None of the hospital staff developed IgG against SARS-CoV-2.


COVID-19 antibody test could detect a substantial number of hospital staffs who could be potential silent spreaders in a province with zero COVID-19 case. Antibody testing should be encouraged for mass screening, especially in asymptomatic healthcare workers.

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