A One-Year Prospective Cohort Study of SARS-CoV-2 Infection and Sociodemographic Factors in Thailand

Abstract

Objective: COVID-19 was declared a global health emergency in January 2020 and a pandemic in March 2020. Although its clinical features and risk factors have been widely studied, most research has relied on retrospective or cross-sectional data, limiting insight into asymptomatic or mildly symptomatic cases. This study aimed to assess the occurrence of SARS-CoV-2 infection and its association with sociodemographic factors in a Thai population. Method: A one-year prospective cohort study was conducted from October 2021 to November 2022 at Prachatipat Hospital, Pathum Thani (N = 202), and Vichaivej International Hospital (Samut Sakhon), Samut Sakhon (N = 212). Adults aged 18–65 years who were asymptomatic at baseline were enrolled and completed self-administered questionnaires at five time points. Sociodemographic, clinical, and vaccination data were analyzed for associations with infection. Results: The cumulative incidence of SARS-CoV-2 infection was 47% at Prachatipat Hospital and 40% at Vichaivej International Hospital (Samut Sakhon). Reinfections occurred in 5.3% and 17.9% of participants, respectively, with no relapses reported. Genomic surveillance identified Delta and Omicron as the predominant variants during the study period. Common symptoms included cough, sore throat, fever, runny nose, and fatigue. Higher infection rates were observed among healthcare workers and individuals with specific sociodemographic profiles. Conclusion: These findings provide important insights into infection patterns and risk factors across diverse Thai populations and may support more targeted public health strategies.