Fig. 5.

These panels show the immunity gap—that is, the difference between vaccine coverage and population immunity—for a variety of target ages and coverages. Here, we are comparing these vaccine schedules in a developing population with 3-month maternal immunity. a At high coverage, all of these vaccine schedules could achieve herd immunity. However, as maternal immunity is less significant at older ages, it has a different effect on the immunity gap at the different ages. Notably, the immunity gap line when vaccinating at the youngest age with high coverage is significantly curved. b Focusing on the immunity gap at coverages that might be maintained in regions with measles elimination, it is clear that 12 months is the best age to vaccinate at all of these coverages in a region with this age structure and maternal immunity decay. However, whether it would be better to miss the target age by vaccinating a little too young (10 months) or a little too old (14 months) depends on coverage, with vaccinating younger ages still being worse at high coverages