About half a million children under five years of age die as a result of rotavirus infection each year. But hopes for a safe and effective vaccine have been raised by two recent studies published in The New England Journal of Medicine (5 January 2006).

The rotavirus vaccines Rotateq (Merck & Co.) and Rotarix (GlaxoSmithKline) reduced the number of cases of severe gastroenteritis in clinical trials by 98% and 85%, respectively. Both vaccines also markedly reduced the number of infants requiring hospital treatment for symptoms of rotavirus infection (which include dehydration and diarrhoea).

Most deaths from rotavirus occur in developing countries, but almost all children worldwide are infected with rotavirus at least once by five years of age. And each year, ∼70,000 children in the United States receive hospital treatment (USA Today, 4 January 2006), as well as ∼1 in 38 children in the United Kingdom by the age of five (BBC News, 5 January 2006).

Researchers have been attempting to develop a rotavirus vaccine since the 1970s. In 1998, RotaShield (Wyeth) was released on the market, but it was withdrawn within a year because a small number of individuals developed an intestinal blockage known as intussusception. Both of the new vaccines were therefore tested on a large number of infants (in Europe, the United States and Latin America). Neither vaccine seemed to cause intussusception. “These are milestone results”, says John Wecker, of PATH (New Scientist, 14 January 2006), a US non-profit organization that is working with Merck & Co. and GlaxoSmithKline to set up trials in Asia and Africa.

Such trials are crucial, as Roger Glass and Umesh Parashar (Centers for Disease Control and Prevention, USA) write in The New England Journal of Medicine (5 January 2006): “Both vaccines will need to demonstrate their efficacy in the difficult settings of developing countries”.