Waning population immunity to measles in Taiwan

► The coverage rate of measles vaccine was >95% for more than a decade in Taiwan. ► We estimated the seroprevalence of measles in Taiwan using volunteer-based samples. ► There was a significant declining trend of seropositivity with age in vaccinees. ► The overall seroprevalence of measles was not sufficient for herd immunity. ► Waning vaccine-induced immunity weakened the population immunity to measles.