Vaccines are among the most effective health tools available: measles vaccination alone is estimated to have saved nearly 59 million lives since 2000. Yet in 2025, WHO and UNICEF estimate that 13.5 million infants did not receive a single dose of the basic diphtheria-tetanus-pertussis (DTP) vaccine. These zero-dose children usually miss every other routine vaccine too. Millions more start their vaccinations but do not finish them: about 7.3 million infants received a first DTP dose but dropped out before their first measles dose. Global coverage has inched up since the pandemic but is still slightly below 2019 levels.
Gaps in protection let diseases return. Measles is so contagious that about 95% of children need two doses to stop outbreaks, but only 84% received a first dose and 77% a second in 2025. An estimated 11 million people were infected with measles in 2024, more than before the pandemic, and about 95,000 died, mostly children under five. Unvaccinated children are concentrated in conflict-affected and fragile settings and in poorer communities, while in some middle- and high-income countries coverage is slipping amid weaker political commitment, structural problems or rising hesitancy, even where vaccines are easy to get. Cuts to international health funding since 2025 are not yet reflected in the latest estimates.
How immunization gaps are measured
Each year WHO and UNICEF estimate national vaccination coverage for infants, combining routine reports from health facilities with household surveys. The Immunization Agenda 2030 and SDG target 3.b track progress with a few core measures:
Zero-dose children
Infants who have not received a first dose of a DTP-containing vaccine by their first birthday. Because DTP is the first routine vaccine in almost every country, missing it is used as a marker for children whom the health system does not reach at all.
Under-vaccinated children (drop-out)
Children who start the schedule but do not complete it, for example those who receive a first DTP dose but not the third, or who never receive a measles vaccine. DTP3 coverage is the standard yardstick for how well a routine programme works.
Measles coverage (MCV1 and MCV2)
The share of children who receive the first and second dose of a measles-containing vaccine. Coverage of about 95% with two doses is needed to prevent outbreaks, which makes measles an early warning signal for gaps in the wider system.
Breadth of protection
Whether children and adolescents also receive newer vaccines, such as those against pneumococcus, rotavirus and the human papillomavirus (HPV), which national schedules have added over the past two decades.