Nigeria has more zero-dose children—defined as not having received the first dose of diphtheria-tetanus-pertussis (DTP) containing vaccine—than any other country in Africa and among the most worldwide. Each year nearly 2.5 million children do not receive DTP1, and in 2020, an additional 500,000 children were unvaccinated as a result of the COVID-19 pandemic. Learn more about the state of routine immunization in Nigeria and the complex reasons why these children are not vaccinated.