Parashar says the vaccines were initially limited to more developed countries, because more testing was needed before they could be used in resource-poor settings.

"In 2009, we actually had data available from these clinical trials in Africa and Asia, and then the World Health Organization expanded to a global recommendation for rotavirus vaccines. So the vaccines are just about to be rolled out over the next two years."

The authors of this new paper say that as the vaccine is rolled out in the developing countries, rotavirus-related deaths should be substantially reduced.

"And so it really highlights the need to introduce these vaccines so we can really reap the full reward of vaccination in reducing diarrheal mortality."

Umesh Parashar and colleagues published the results of their study online in The Lancet Infectious Diseases.