Temporary Fertility Decline after Large Rubella Outbreak, Japan.

Japan experienced 2 large rubella epidemics in 2004 and 2012-2014. Because of suboptimal immunization levels, the country has been experiencing a third major outbreak during 2018-2020. We conducted time series analyses to evaluate the effect of the 2012-2014 nationwide rubella epidemic on prefecture-level natality in Japan. We identified a statistically significant decline in fertility rates associated with rubella epidemic activity and increased Google searches for the term "rubella." We noted that the timing of fertility declines in 2014 occurred 9-13 months after peak rubella incidence months in 2013 in 4 prefectures with the highest rubella incidence. Public health interventions should focus on enhancing vaccination campaigns against rubella, not only to protect pregnant women from infection but also to mitigate declines in population size and birth rates.