Conflicts have hampered efforts to vaccinate children across the world, health leaders have warned, as new figures showed about 14.5 million children had not received a single immunisation dose.

More than half of the children live in countries where armed conflicts or other humanitarian crises had created fragile and vulnerable situations, according to data from the UN children’s agency, Unicef, and the World Health Organization.

The war in Sudan has led to a huge rise in numbers of unvaccinated children, from about 110,000 in 2021 to an estimated 701,000 last year. Yemen has 580,000 unvaccinated children, up from 424,000 three years ago.

In addition to the 14.5 million “zero-dose” children in 2023, 6.5 million children were “under-vaccinated”, meaning they had not received all their recommended doses.