A rise in uncertainty tends to reveal innate heterogeneous preferences. We use the COVID-19 pandemic to measure how Japanese adults’ preferences for policies to combat COVID-19 evolved from July 2020 to February 2021 using an internet panel randomized conjoint experiment where participants chose between hypothetical policy packages intended to combat COVID-19. In July 2020, Japanese adults showed divergent preferences on the critical element of the security-liberty trade-o↵ in terms of the government’s tracking of social media/phone communication records as a measure to detect infection routes. In February 2021, after factoring in estimated risks of infections, death tolls, and the progress of vaccination, Japanese adults converged to restore the value to defy the government’s tracking of social media/phone communication records.