Nigeria has the most children unvaccinated and under-vaccinated against measles in the world, despite a global decline in deaths from the dangerous but preventable disease.
In Nigeria, nearly four million children under one year missed out on the first dose of the vaccine against measles in 2017 alone.
The United Nations Children's Fund (UNICEF) confirmed the statistics while commemorating the World Immunisation Week on Thursday.
The data had been previously reported by the World Health Organisation (WHO).
"In 2017, for example, Nigeria had the highest number of children under one year of age who missed out on the first dose, at nearly four million", UNICEF's Executive Director, Henrietta Fore, said at the opening of the event marked annually between April 24 and 30.
"It was followed by India (2.9 million), Pakistan and Indonesia (1.2 million each), and Ethiopia (1.1 million)."
The News Agency of Nigeria (NAN) reported that measles is a highly contagious disease that accounts for 13 per cent of all vaccine-preventable deaths in children younger than five years in Africa.
The disease infects nine in ten people who are not vaccinated.
Two doses of the measles vaccine are essential to protect children from the disease.
The UNICEF director said the global coverage of the first dosage is still below the recommended benchmark, while that of the second "is even more alarming."
"Of the top 20 countries with the largest number of unvaccinated children in 2017, nine have not introduced the second dose.
"Twenty countries in sub-Saharan Africa have not introduced the necessary second dose in the national vaccination schedule, putting over 17 million infants a year at higher risk of measles during their childhood, " Ms Fore said.
Since 2000, an estimated 5.5 billion doses of measles-containing vaccines have been provided for children through routine immunisation services and mass vaccination campaigns.
This has saved an estimated 20.4 million lives, according to a joint report by some leading health organisations, including WHO and UNICEF.
The report published two years ago by this newspaper said there was a decline in global death from the disease in 2016 as an estimated 90,000 people died from measles. This is about 84 per cent drop from the more than 550,000 deaths in 2000.
However, a 2017 WHO report indicated that 20.8 million children are still missing their first measles vaccine dose and more than half of these unvaccinated children live in Nigeria and five other countries.
Since measles is a highly contagious viral disease, outbreaks continue to occur in Nigeria despite efforts by government, local and international health organisations to improve vaccination across the country.
On Wednesday, Punch newspaper reported that WHO listed Nigeria among nine African countries with fresh measles outbreaks this year.