In the 4th outbreak of the covid-19 pandemic in Ho Chi Minh City since 27 April 2021, asymptomatic or mild covid-19 patients were self-quarantined and treated at home. This home care setting could yield risk of SARS-CoV-2 transmission from the index cases to the people living surroundings. Therefore, this study will be performed to investigate the immunogenicity against SARS-CoV-2 in household members or people lived in the same municipality with home-quarantined covid-19 patients.~All people over 18 years old, living in 2 blocks (V and Y) of Ngo Gia Tu apartment, which is located in District 10, Ho Chi Minh City, will be recruited into this study. A survey will be conducted using a questionnaire to collect the data related to the basic demographic information, medical history of SARS-CoV-2 infected individuals, exposure history of close contacts, vaccination status, and compliance with the strategies for self-quarantine to prevent the transmission in the community.~At the time of recruitment, Covid-19 rapid antigen detection tests using nasopharyngeal swabs will be performed for all study subjects. In addition, a total of 5mL of intravenous blood samples will be collected for serum extraction and DNA isolation. SARS-CoV-2 neutralizing antibody levels in serum samples will be evaluated by a surrogate virus neutralization test by using NeutraLISA kit® (Euroimmun, Luebeck, Germany). DNA will be isolated and stored for further use in investigating the association of ACE2 genetic polymorphisms with the prevalence of SARS-CoV-2 neutralizing antibodies.
This study will investigate the presence of SARS-CoV-2 neutralizing antibody and its association with demographic information, medical history of SARS-CoV-2 infected individuals, exposure history of close contacts, vaccination status, and compliance with the strategies for self-quarantine to prevent the transmission in the community where SARS-CoV-2 infected individuals were home-quarantined and treated.