12). However, the temporal variations of psychobehavioral responses have not been examined. In addition to psychobehavioral responses, unique to COVID-19 is its unprecedented massive epidemic size compared with other recent outbreaks, such that vaccination becomes the exit strategy. However, despite vaccine availability, vaccine doubters may hamper the global effort against COVID-19 ( 13). Unraveling the reasons behind vaccine hesitancy and monitoring its trends over time will support the design of interventions to boost COVID-19 vaccine uptake. We report a longitudinal analysis of 5 representative population-based surveys of adults in Hong Kong on their psychological, behavioral, and vaccine-related responses, conducted during the first 2 waves of the COVID-19 epidemic. Our main objectives were tracking major psychobehavioral responses (including risk perception, psychological distress, and adoption of precautionary measures) over time and examining the determinants of the intention to receive the COVID-19 vaccine. As a complement, other psychobehavioral responses (such as knowledge about COVID-19) were also reported. These findings should have major implications for infection control policies and targeted mental health recommendations. Hong Kong has a high-income economy but had major social unrest in the prepandemic period in the population (