Abstract
BACKGROUND: Public health and social measures are crucial for controlling the spread of pathogens. However, well-tailored assessments of their impact remain elusive, particularly considering time-varying immunity established from prior exposures and its waning. METHODS: We developed a mathematical model to estimate the time-varying basic reproduction number, accounting for the dynamics of underlying immunity. Applying this framework, we retrospectively assessed the impact of public health and social measures implemented from November 2021 to April 2022 on SARS-CoV-2 transmission in Korea and discussed potential biases from ignoring underlying immunity. RESULTS: Our proposed model estimated a notable attenuation in the impact of public health on social measures on SARS-CoV-2 transmission in Korea with the emergence of the Omicron variants while remaining effective throughout the Delta and Omicron periods. These changes during the Omicron period became evident only upon adjusting for underlying immunity and were correlated with observed human mobility patterns in Korea. CONCLUSIONS: Our findings support the importance of incorporating underlying immunity in evaluating public health and social measures, particularly in the presence of substantial changes over a short period, such as widespread infections or vaccination. This model would stand as a tool for informing public health planning, capable of mitigating the overall disease burden in future epidemics.