A vaccine against rotavirus drastically reduced the death toll from childhood diarrhea in Venezuela, according to a study published in tomorrow's issue of the New England Journal of Medicine. But critics say the vaccine's efficacy still hasn't been confirmed in the poorest of countries, where inadequate nutrition might work against it, and they argue that most developing countries won't be able to afford it anyway.
Nearly 900,000 infants and children die every year, mostly in the developing world, from severe diarrhea caused by rotavirus infections. Although the virus infects almost everyone in the world, it kills only children. A child with severe rotavirus diarrhea may suffer 10 to 15 bouts of diarrhea and vomiting each day. And although treatment with rehydration salts and proper food can save lives, researchers have been working for years on a vaccine that could reduce the severity of the disease, especially in developing countries with poor health care and nutrition.
In the early 1990s, Albert Kapikian and his colleagues at the National Institute of Allergy and Infectious Diseases developed such a vaccine, and tests in Finland and the United States showed that it could cut the incidence of severe diarrhea. But in tests in developing countries such as Brazil and Peru, it reduced cases by only 30% to 45%. Kapikian and his colleagues decided to set up their own vaccine trial in a poor urban area near Caracas, Venezuela, with a 10-fold stronger dose of the vaccine.
In contrast with earlier trials--which counted every case in which a child got sick and thus would not have detected a reduction in the severity of the disease--the researchers only tallied the number of cases in which a child was hospitalized with severe diarrhea. In the study of 2200 infants, the vaccine reduced the incidence of severe disease by 88% compared with the control group. The only side effect of the vaccine was a mild fever.
But other diarrhea researchers say that the vaccine's effectiveness in Venezuela doesn't mean that it will work everywhere. Richard Cash, of Harvard School of Public Health and Harvard Institute for International Development, says the impressive results in Venezuela could be due to better nutrition that bolsters immune systems, and a lower overall diarrhea rate than Brazil or Peru. "What you really need to do is try it out in Bangladesh or in a sub-Saharan African country where the sanitation is the worst," he says. Cash also points out that at $30 a dose, the vaccine is too expensive for many developing countries, where the annual health care spending averages only $5 to $20 per person.