The number of mortalities from measles over that period fell from 542,000 to 158,000, it said in a statement on Thursday.
The number of new cases fell by 58 percent to 355,000 in 2011.
The UN health agency recommends that all children receive two doses of measles vaccine to be protected from the highly contagious disease.
But despite high-profile vaccination campaigns, the vaccine has yet to reach all those in need.
The WHO estimates that 20 million children worldwide failed to receive first dose of the vaccine in 2011.
More than half live in India (6.7 million children), Nigeria (1.7 million), Ethiopia (one million), and Pakistan (900,000) and the Democratic Republic of Congo (800,000).
In 2011, these five countries experienced large outbreaks of measles, while thousands of cases were also recorded in other countries including France, Italy and Spain.
Most of these countries have committed to eradicating measles by 2015 or 2020.