Projected sudden step-wise increase in risk of large measles outbreaks in the Netherlands as susceptible children enter secondary school in 2025/26

Background Many unvaccinated children were naturally immunised through infection during the last national Measles epidemic in the Netherlands (2013/14). Over time susceptibility amongst school aged children in key under-vaccinated populations is likely to increase and warrants investigation. Methods We constructed a network to reflect the risk of transmission within and between schools in the Netherlands. Estimating school-level susceptibility rates using historical estimates and vaccine uptake. We evaluated the annual outbreak risk since 2014 projecting to 2030. Results As children born since the 2013/14 outbreak enter secondary school, the connectedness of the school-mediated contact network between susceptible children will increase sharply, resulting in a sudden increase in the risk of large measles outbreaks. Conclusions We anticipate a substantial increase in the risk of large measles outbreaks mediated by school-based transmission in 2025 and 2026 as larger numbers of susceptible children enter secondary school.