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

Abstract

Background: As a response to the coronavirus disease 2019 (COVID-19) pandemic, Vietnam enforced strict quarantine, contact tracing and physical distancing policies. By December 2020, this strategy resulted in one of the lowest numbers of individuals infected with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) cases globally. This study aimed to determine the prevalence of SARS-CoV-2 antibody positivity among high-risk populations in Vietnam.Methods: A prevalence survey was undertaken within four communities in northern and central 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 that evaluated exposure history. SARS-CoV-2 IgG antibodies were quantified using a commercially available assay.Results: 3056 community members and 149 health care workers provided consent to participate. Among enrolled community members, 27 (0·9%) were household contacts and 53 (1·7%) were close contacts. Serology was performed in 3034 individuals. 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 14·9 to 15·2) weeks after exposure.Conclusion: The presence of SARS-CoV-2 antibodies in high-risk communities and healthcare workers was low in communities in Vietnam with known COVID-19 cases. The public health response to the COVID-19 pandemic in Vietnam has been effective in limiting community transmission of SARS-CoV-2.Funding Statement: This project was supported by a grant funded by the Australian Department of Foreign Affairs and Trade, awarded in conjunction with the Australian National Health and Medical Research Council (APP1153346).Declaration of Interests: None declared.Ethics Approval Statement: Ethical approval was obtained from the Human Research Ethics Committees of the University of Sydney (HREC 2020/415) and Biomedical Research Ethics Committee of the National Hospital for Tropical Diseases (No. 10/HDDD-NDTU and No. 18/HDDD-NDTU). Consent was documented electronically using a tablet computer. In accordance with local expectations, all COVID-19 patients and other participants were provided with monetary compensation for their participation, equivalent to approximately US$4·30 and US$2·20, respectively.