Vaccines against rotavirus, which can kills babies and young children within days by causing severe diarrhea, could save 2 million children over the next decade, experts said Wednesday.

Two studies published in the New England Journal of Medicine showed that vaccinating babies against rotavirus significantly cut deaths from diarrhea — by 61 percent in Africa and by 35 percent in Mexico.

"Widespread use of these vaccines has the potential to prevent about 2 million deaths over the next decade," Dr. Mathuram Santosham of Johns Hopkins University in Baltimore, who was not involved in the studies, wrote in a commentary.

"The vaccines should be introduced immediately in areas with high mortality from rotavirus infection."

Rotavirus is the leading cause of severe diarrhea, which kills more than 500,000 children under 5 every year, nearly half of them in Africa. Rotavirus vaccines are now given as part of the standard immunizations in developed countries such as Canada and the United States.

Merck and Co makes a rotavirus vaccine called RotaTeq and GlaxoSmithKline makes one called Rotarix.

"In Mexico, which in 2006 was among the first countries in the world to introduce rotavirus vaccine, diarrheal disease death rates dropped during the 2009 rotavirus season by more than 65 percent among children age 2 and under," the non-profit organization PATH and the GAVI Alliance, both of which promote vaccination in the developing world, said in a joint statement.

"This demonstrates real-world impact that is crucial as other countries consider rotavirus vaccine introduction."

For one of the studies, Dr. Kathleen Neuzil of PATH and the University of Washington and colleagues tested more than 4,000 infants in South Africa and Malawi, giving either Glaxo's oral rotavirus vaccine or a placebo.

Nearly 5 percent of the babies given a placebo developed severe diarrhea, compared to 1.9 percent of those who got the vaccine, they said — a 61 percent efficacy rate.

WORLDWIDE DISTRIBUTION

"GSK is committed to working with our partners to help ensure that Rotarix reaches those in need, wherever they live," Glaxo's Thomas Breuer said in a statement.

For the study in Mexico, Dr. Manish Patel of the U.S. Centers for Disease Control and Prevention and colleagues studied diarrhea and rotavirus cases in Mexico before and after rotavirus vaccines were introduced.

"Mexico had previously instituted interventions, including improved sanitation, use of oral rehydration, breastfeeding, and vitamin A supplementation, but diarrhea-related deaths during the December-to-May rotavirus season still remained high," Patel said in a statement.

By December 2007, 74 percent of babies had received at least one dose and in 2008, there were 1,118 diarrhea-related deaths among children younger than 5, which was 675 fewer than in 2006.

"The reduction in mortality following vaccine introduction points to the importance of immunization against rotavirus as a primary prevention tool in controlling diarrhea not just in Mexico but around the world," Patel said.

"The next challenge is to ensure that rotavirus vaccines reach all those in need," said Dr. Tachi Yamada of the nonprofit Bill & Melinda Gates Foundation.