The persistence of measles in many regions demonstrates large immunity gaps, resulting from incomplete or ineffective immunization with measles-containing vaccines (MCVs). A key factor affecting MCV impact is age, with infants receiving dose 1 (MCV1) at older ages having a reduced risk of vaccine failure, but also an increased risk of contracting infection before vaccination. Here, we designed a new method—based on a transmission model incorporating realistic vaccination delays and age variations in MCV1 effectiveness—to capture this risk trade-off and estimate the optimal age for recommending MCV1. We predict a large heterogeneity in the optimal ages (range: 6–20 months), contrasting the homogeneity of observed recommendations worldwide. Furthermore, we show that the optimal age depends on the local epidemiology of measles, with a lower optimal age predicted in populations suffering higher transmission. Overall, our results suggest the scope for public health authorities to tailor the recommended schedule for better measles control.

The authors have declared no competing interest.

This work was supported by the Max Planck Society (Berlin, Germany).

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