Incidence of Type 1 Diabetes in Relation to Exposure to Rotavirus Infections in Pre-and Postvaccine Birth Cohorts in Finland

OBJECTIVE To explore the incidence of type 1 diabetes in children in relation to exposure to rotavirus infections. RESEARCH DESIGN AND METHODS A nationwide register-based ecological study on the 1995–2015 birth cohorts in Finland compared those born before and after the national implementation of the rotavirus vaccine in 2009. RESULTS When the prevaccine 2001–2005 birth cohorts were compared with the postvaccine birth cohorts, the number of children exposed to rotavirus infection by the age of 5 years decreased from 2,522 per 100,000 children (2.5%) to 171 per 100,000 children (0.2%), while the incidence of type 1 diabetes in those aged <5 years decreased from 71.5 to 54.4 per 100,000 person-years (incidence rate ratio 0.79, 95% CI 0.71–0.86). CONCLUSIONS At the population level, a decrease in exposure to rotavirus infections was associated with a decrease in the incidence of type 1 diabetes in young children.