The study examined population immunity against serotype 2 poliomyelitis induced by inactivated vaccine (IPV) in 112 countries. The researchers combined data on vaccine effectiveness with age, vaccination coverage and national vaccination schedules using a mathematical model. According to current plans, median population immunity among children under five will be 61% in 2025, rising to 71% in 2031. The study found that a vaccination schedule with the first dose at 14 weeks of age and the second dose between 14 and 39 weeks is optimal in all countries and could increase immunity to 85% by 2031. Eight countries would still have less than 50% immunity, which could be increased to 65 to 72% through catch-up campaigns with 80% coverage in 2030. The authors conclude that IPV schedules and coverage in many countries are suboptimal and recommend changes in vaccination schedules and the implementation of catch-up campaigns.