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

A decade has passed since the last major measles epidemic amongst the undervaccinated Dutch orthodox protestant community, when the majority of unvaccinated children were naturally immunised through infection. Using national school data, we demonstrate that, in September 2026, the entry of children born since the 2013/14 outbreak into secondary school could facilitate a rapid increase in the connectedness of the school-mediated contact network between susceptible children resulting in a sharp increase in the risk of large (over 1000-cases) measles outbreaks.