At the launch of the ninth African Vaccination Week on Wednesday in São Tomé and Príncipe, immunisation partners stressed the importance of countries remaining vigilant in the fight against vaccine-preventable diseases.
The United Nations Children's Fund is warning that cases of measles around the world have almost trebled compared with the same period past year.
The UNICEF report said an estimated 169 million children missed out on the first dose of the measles vaccine between 2010 and 2017 - equating to 21.1 million children a year on average.
Typically, two doses of the measles, mumps, rubella (MMR) vaccine are required to prevent a child from contracting either disease. The first is normally given at age 12-15 months, while the second is administered between 4 and 6 years of age. However, UNICEF also notes that both "complacency" and "fear of skepticism about vaccines" are partly to blame.
"The measles virus will always find unvaccinated children", said Ms Henrietta Fore, executive director of the United Nations Children's Fund (Unicef).
"If we are serious about averting the spread of this risky but preventable disease, we need to vaccinate every child, in rich and poor countries alike", she said. The global coverage for this second dose is about 67 per cent.
The WHO recommends a threshold of 95 percent immunisation coverage to achieve so-called "herd immunity" - or vaccinating a significant enough portion of the population to provide protection for those who have yet to develop immunity. Therefore, their health depends on everyone else receiving the vaccine.
In 2017, for example, Nigeria had the highest number of children under one year of age who missed out on the first dose, at almost 4m.
France and the United Kingdom followed the U.S.in child vaccine gaps, with 608,000 and 527,000 unvaccinated respectively within the eight-year period. Adults should be vaccinated with at least one dose of MMR vaccine, and those with higher risk, such as worldwide travelers and health-care workers, should receive a second dose.
In low- and middle-income countries, the situation is critical.
The data clearly shows that vaccine coverage varies greatly between countries and that work still needs to be done to bring vaccines to all.
Germany ranks eighth among high-income countries with 168,000 cases of children missing the first dose.
The rising numbers of unvaccinated children is attributed to the rise of a "vaccine rejection" trend among some parents in developed countries, including a militant "anti-vax" movement which spreads myths and untruths about vaccine safety.