Quantifying social contact dynamics in South Korea in the post-COVID-19 endemic phase: A cross-sectional survey for infectious disease transmission

Background: Understanding the dynamics of social contact patterns is crucial for modeling the spread of infectious diseases. Although previous studies have examined them globally, how relevant they are to social patterns in the endemic phase is still unclear. South Korea's distinct cultural norms, aging population, and declining fertility highlight the critical need for new, context-specific data. Here, we aim to conduct a contact survey in South Korea, providing age and location-specific contact estimates and quantifying patterns related to infectious disease transmission. Methods: We conducted a cross-sectional survey in South Korea from July 6 to September 5, 2023. Participants of all ages were recruited using quota sampling based on the 2023 census, with only one individual per household included. Social contacts, both physical and non-physical, were recorded through a 24-hour diary. The data were analyzed with a negative binomial regression model. Age-specific contact matrices were constructed using census-based sampling weights, with uncertainty assessed through bootstrapping. Results: A total of 1493 participants (740 males and 753 females) reported 14,187 contacts, with an average of 9.2 daily contacts (95 % confidence interval [CI]: 8.7–9.8). Contacts peaked at 17.8 (95 % CI: 14.6–21.5) among children aged 5–9 and were lowest at 3.5 (95 % CI: 2.6–4.5) for those aged 75 and above. Children and teenagers had a higher rate of peer-group contact, with most contacts occurring in workplaces or educational institutions. The level of family contact increased across all age groups. Conclusion: We identified distinct social contact patterns in South Korea, such as high interactions within peer groups, which suggest the need for school-based vaccination programs, family-centered strategies, and workplace infection control measures. These findings provide critical baseline data to enhance disease modeling and inform professional public health policy development in South Korea and other cultural contexts.