The number of measles deaths worldwide has apparently dropped by about three-quarters over a decade, according to a new study by the World Health Organization and others.

Most of the deaths were in India and Africa, where not enough children are being immunized.

Health officials estimate about 9.6 million children were saved from dying of measles from 2000 to 2010 after big vaccination campaigns were rolled out more than a decade ago. Researchers guessed the number of deaths fell during that time period from about 535,300 to 139,300, or about 74 percent.

But the figures come with a big grain of salt; scientists only had solid data for 65 countries. For the 128 others, they used modeling to come up with their estimates.

Despite the major dent, the progress fails to meet a WHO target to cut measles deaths by 90 percent by 2010.

"This is still a huge success," said Peter Strebel, a measles expert at WHO and one of the authors of the study. "You don't reduce measles deaths by three quarters without significantly accelerating efforts."

He noted that the global 85 percent vaccination coverage rate was the highest ever recorded.

The study was paid for by the U.S. Centers for Disease Control and Prevention and was published Tuesday in the journal, Lancet.

Measles is one of the most infectious diseases that exists and mostly affects children. It causes a fever, cough and a rash all over the body. The disease kills about one to two children for every 1,000 it infects and can also cause pregnant women to have a miscarriage or premature birth.

Past progress in reducing measles has led some health officials to consider whether they can eradicate it. Smallpox is the only human disease to have been wiped out. Other initiatives to rid the world of diseases including polio and guinea worm remain largely stalled.

"I am cautious about adopting too many eradication campaigns at once," said Nancy Leys Stepan, author of a book on disease eradication and a professor at Columbia University. She was not linked to the study.

Stepan said problems like getting good data and the challenges of eradication make it more reasonable to stick to deadlines for reducing measles rather than trying to eliminate it.

In recent years, the disease has surged in Europe — the number of people infected since 2007 has tripled. Doctors say measles cases are rebounding in Europe because people don't realize how serious the disease is and are skeptical of the vaccine.

The first measles shot was licensed in the U.S. in 1963 and is now widely included in routine childhood immunization programs in developed countries. Last year was the worst year for measles in the U.S. in 15 years, with 222 cases — mostly imported by foreign visitors or by U.S. residents infected overseas.

Daniel Berman, a vaccines expert at Medecins Sans Frontieres, noted there has been a massive increase in measles across Africa in the last two years, largely because of backsliding on immunization campaigns and declining funds.

"The challenge is to find ways to make measles campaigns happen in countries with weak systems," he said.

Berman said it would be hard to dramatically improve the 74 percent drop in measles deaths and that it would probably plateau.

WHO's Strebel said just maintaining the decline in measles still requires a major effort. He added experts are not ready to set any eradication deadlines.

"Let's wait until we get a bit closer to the top of the mountain before we say if we can get there," he said.