American and British drug companies have developed new diarrhea vaccines that proved highly effective in early testing against this often deadly disease. The tests show the vaccines appear not to have the harmful side-effect that forced withdrawal of the first diarrhea vaccine seven years ago and could save hundreds of thousands of children's lives each year.
Extreme diarrhea caused by the rotavirus is the second leading cause of death in children under five. It affects 130 million infants a year worldwide, killing more than 500,000 through dehydration, mainly in developing countries. But it is also a significant cause of hospitalization and visits to pediatricians for infants in North America and Europe.
Global efforts to control this disease suffered a setback in 1999 when production of the first vaccine licensed to fight rotavirus was halted by the U.S. manufacturer, Wyeth-Lederle. It was linked to a bowel obstruction affecting one of every 10,000 vaccinated infants.
Now the U.S. company Merck and its British counterpart GlaxoSmithKline have each developed new diarrhea vaccines that have performed well in two separate tests involving more than 60,000 babies in Latin America, the United States and Finland.
"This could have a major impact to improve the health of children in developing countries as well as in the developed world," said physician and virus expert Roger Glass of the U.S. government's disease tracking agency, the Centers for Disease Control (CDC).
"Rotavirus is an infection that every child gets in his first few years of life, so that American children who are hospitalized or seek physician's care as well as Bangladeshi children who might die of this infection can all benefit from a rotavirus vaccine," he added.
According to reports in the New England Journal of Medicine, the two vaccines, taken orally, were between 85 and 98 percent effective in children under one year of age. They reduced hospitalizations between 42 and 63 percent. Both caused no more risk for the bowel obstruction than a dummy vaccine.
But Dr. Glass warns that the new products must still stand the test of real-world use over time.
Both contain live, but weakened viruses to stimulate an immune response. The aim is to train the immune system to recognize and block a real rotavirus infection. But Dr. Glass says children in poor regions of the world may have conditions that could foil the effect.
"Children in developing countries have lots of stomach infections and intestinal infections," he added. "They have different food items, allergies, malnutrition, which can all affect the way the virus behaves in replicating and giving a good immune response. So until we have good data from poor children in developing countries where rotavirus is a killer, we will not know how well these vaccines will prevent death in those children."
The U.S. public health official says further trials of the GlaxoSmithKline diarrhea vaccine have begun in South Africa and will soon be carried out in Bangladesh and Malawi.
Dr. Glass points out that the World Health Organization and donor groups are supporting the vaccines' introduction in developing nations. He adds that once the vaccines are proven safe and effective everywhere, mechanisms to ensure their continued supply and affordability should become a global priority.