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. 2022 May;27(5):515-521.
doi: 10.1111/tmi.13744. Epub 2022 Mar 25.

Seroprevalence of SARS-CoV-2 among high-density communities and hyper-endemicity of COVID-19 in Vietnam

Van Thuan Hoang  1 , Thi Dung Pham  1 , Quoc Tien Nguyen  1 , Duy Cuong Nguyen  1 , Duc Thanh Nguyen  1 , Thanh Binh Nguyen  1 , Thi Khanh Thu Tran  2 , Trong Lan Phan  3 , Phan Le Nguyen Vo  4 , Thi Loi Dao  1 , Florence Fenollar  5   6 , Philippe Gautret  5   6
Affiliations

Seroprevalence of SARS-CoV-2 among high-density communities and hyper-endemicity of COVID-19 in Vietnam

Van Thuan Hoang et al. Trop Med Int Health. 2022 May.

Abstract

Objective: To assess the magnitude of active and recovering COVID-19 patients among at-risk communities and to identify the factors associated with positive serology.

Methods: Four hundred and eighty-three close contacts of COVID-19 patients residing in Ho Chi Minh City, Vietnam, during the fourth wave of the COVID-19 epidemic (September and October 2021) were included. Five weeks after exposure to a COVID-19 patient, they underwent a serology test using the BIOSYNEX COVID-19 BSS kit.

Results: The median age of participants was 37 years. A total of 34.6% individuals presented at least one clinical symptom between the time of contact with the COVID-19 patient and inclusion in study. A total of 1.7% unvaccinated individuals tested positive for SARS-CoV-2 using real-time PCR, and 9.5% had evidence of recent infection (positive PCR and/or IgM). A further 26.7% unvaccinated individuals presented evidence of a past infection (positive IgG only). Socio-demographic characteristics, vaccination status and clinical symptoms were not associated with a positive IgM test.

Conclusion: This is the first serosurvey conducted during the fourth wave of the epidemic in Vietnam. It revealed a seropositivity rate higher than in previous studies and confirmed the hyperendemicity of SARS-CoV-2. Testing using rapid serological tests proved to be a reliable, easy-to-use method and enabled a rapid estimation of the burden of COVID-19.

Keywords: COVID-19; SARS-CoV-2; Vietnam; high-density communities; seroprevalence.

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