Measles, which mostly strikes youngsters, can easily be prevented through vaccination. It claimed 873,000 lives in 1999, but the toll was down to 530,000 by the end of 2003, the U.N. agencies said.
"Progress of this magnitude is remarkable," said WHO chief Dr. Lee Jong-wook. "I am certain that with increased commitment from governments and further support from the international community, even more can be accomplished."
Africa remains the hardest-hit continent, but even there, the number of cases has fallen 46 percent due to mass vaccinations.
The U.N.-led campaign aims to halve global measles deaths by the end of this year.
Measles, a viral disease, is spread by infected droplets produced by sneezing and coughing. It causes fever and rash and is sometimes complicated by ear infections, pneumonia or inflammation of the brain, which can result in convulsions, deafness, mental retardation or death.
A decade ago, the disease killed millions of children each year and affected tens of millions more, leaving many with lifelong disabilities.
"In many places where families once lived in fear of losing their children to measles, they're now protected by an effective and inexpensive vaccine," said Carol Bellamy, head of UNICEF. "What clearer proof could there be of the value of investing in immunization?"
It costs around 25 cents to immunize a youngster. Because this is beyond the budget of many poor countries, they have been helped by the U.N. campaign.
The campaign aims to ensure 90 percent of children are immunized before they are 9 months old, with booster vaccinations every three or four years until age 14. The program has reached more than 150 million children since it was launched in 2001.
The campaign's success means measles wards have closed across Africa, freeing up funds to save children from other diseases, WHO and UNICEF said.
Late in 2004, more than 95 percent of children in the African nation of Togo received vaccines to prevent measles and polio, mosquito nets to stop the spread of malaria, and tablets against worms.
Despite the advances, millions of children remain at risk from measles, said the U.N. agencies. Malnourished and un-immunized children under age 5, especially babies, are particularly vulnerable.
Worldwide, more than 130 million children are born every year, mostly in poor nations. "We must reach each and every one with measles vaccination," said Lee.
The United Nations' anti-measles campaign has gathered $144 million since it began, using its own funds as well as donations from the Red Cross, the U.S. Centers for Disease Control and Prevention, the Geneva-based Global Alliance for Vaccines and Immunization, the Bill & Melinda Gates Foundation and the governments of Australia, Canada, Japan and Britain.
By Jonathan Fowler