Nearly 100 million children in China will be vaccinated against measles this month to help eliminate the disease, a leading cause of avoidable death and disability in developing countries, the WHO said on Wednesday.

There were more than 52,000 cases of measles in China in 2009. Although most people recover from the highly contagious viral disease, some suffer serious complications like blindness, encephalitis, severe diarrhea, pneumonia and ear infections.

Michael O'Leary, the World Health Organisation's representative in China, said China's measles cases made up 86 percent of all cases in the western Pacific.

Vaccinating every child, even those who have been vaccinated in the past, is essential in stopping the virus with a wall of immunity in the population, he said in a statement.

O'Leary said residents of remote areas, huge urban expanses and the large migrant population may have less access to vaccines and not be protected against measles.

Globally, 164,000 people died from measles in 2008 - mostly children under the age of five, or 18 deaths every hour.

To eliminate measles, every child should get two doses, the second given after the age of one year.

David Hipgrave, chief of health and nutrition at UNICEF China (United Nations Children's Fund), said the Chinese campaign would be a single-dose exercise.

It's a catch-up campaign to boost the levels of immunity among children who may have missed the second dose, or in whom one of the doses was not effective, he said.