Ongoing threat of a large-scale measles outbreak in Yemen

A year into the protracted and increasingly bloody conflict in Yemen, a sharp decline in coverage of measles and rubella vaccination poses a substantial threat to population health. Falls to around 54% coverage nationally by late 2015 have been noted elsewhere,1 but data available to us from sources in Yemen indicate that coverage might in fact have fallen to as little as 41%. This represents a sharp fall in a very short time period, to a level well below the herd immunity threshold, and in marked contrast to national rates that had hovered fairly consistently between 70% and 80% for the preceding decade or more despite periodic instability in Yemen (especially in the far north) and long-standing access difficulties, especially for rural communities.