Affordable vaccine maker Serum Institute of India has new results to trumpet from a phase 3 trial of its heat-stable rotavirus vaccine as it preps to deliver millions of doses to a national vaccine program.

The company's vaccine, Rotasiil, reduced severe rotavirus diarrhea in infants by 39.5% over two years, according to phase 3 results published in the journal Vaccine. The vaccine was about 55% effective against the most severe cases of rotavirus, which can be fatal. Investigators tested the shot in 7,500 infants at six sites in India.

International nonprofit PATH partnered on the study and another trial that's designed to secure WHO prequalification for the shot. Securing that nod would make the affordable rotavirus shot eligible for purchase and distribution on a global basis. Already, though, India's government has ordered 3.8 million doses of Serum's oral vaccine that's administered in three doses at 6, 10 and 14 weeks of age.

Serum Institute says it has manufactured those doses and is awaiting directions for delivery. The Indian vaccine giant is prepping for a launch on the private market later this year. India approved the shot in January after reviewing previous phase 3 data and inspecting the company's manufacturing operation. PATH's Center for Vaccine Access and Innovation director, David Kaslow, said in a statement the new trial results and vaccine licensure are an "encouraging milestone toward the public health goal of improving the supply of affordable rotavirus vaccines, both in India and worldwide." Kaslow in an email called the vaccine's success a "double win" because "India now has another proven tool to combat rotavirus and the vaccine is manufactured in-country." He added that the country's immunization program could reach 26 million children.

In a separate phase 3 study in Niger, investigators reported that the vaccine was 67% effective against severe rotavirus gastroenteritis in infants. The results were slightly better than the 61% posted by GlaxoSmithKline’s Rotarix and much better than the 39% demonstrated by Merck’s RotaTeq, both in previous trials. Those vaccines need to be refrigerated.

India suffered more than 47,000 deaths due to rotavirus in 2013, according to PATH's release, or more than a fifth of the rotavirus deaths around the world that year.