Sero-Prevalence of SARS-CoV-2 Antibodies in High-Risk Populations in Vietnam

Hasan, Tasnim; Pham, Thach Ngoc; Nguyen, Thu Anh; Le, Hien Thi Thu; Van Le, Duyet; Dang, Thuy Thi; Van, Trang Dinh; Pham, Yen Ngoc; Nguyen, Ha Viet; Tran, Giang Linh; Nguyen, Van Thi Cam; Nguyen, Thanh Trung; Truong, Viet Quang; Dao, Than Huu; Le, Chung Thanh; Truong, Nam Tan; Vo, Hoang Trung; Le, Phuc Thanh; Nguyen, Thao Thanh; Van Luu, Vinh; Nguyen, Vinh Dai; Toelle, Brett G.; Marks, Guy B.; Fox, Greg J.

As a response to the coronavirus disease 2019 (COVID-19) pandemic, Vietnam enforced strict quarantine, contact tracing and physical distancing policies resulting in one of the lowest numbers of individuals infected with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) globally. This study aimed to determine the prevalence of SARS-CoV-2 antibody positivity among high-risk populations in Vietnam. A prevalence survey was undertaken within four communities in Vietnam, where at least two COVID-19 cases had been confirmed. Participants were classified according to the location of exposure: household contacts, close contacts, community members, and healthcare workers (HCWs) responsible for treating COVID-19 cases. Participants completed a baseline questionnaire and SARS-CoV-2 IgG antibodies were quantified using a commercial assay. A total of 3049 community members and 149 health care workers consented to the study. Among 13 individuals who were seropositive (0.4%), five household contacts (5/27, 18.5%), one close contact (1/53, 1.9%), and seven community members (7/2954, 0.2%) had detectable SARS-CoV-2 antibodies. All HCWs were negative for SARS-CoV-2 antibodies. Participants were tested a median of 15.1 (interquartile range from 14.9 to 15.2) weeks after exposure. Our study found a low prevalence of SARS-CoV-2 antibodies in high-risk communities and healthcare workers in communities in Vietnam with known COVID-19 cases.