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A trial of a rotavirus vaccine in children in ten Latin American countries has shown it to be effective at the ages children are most vulnerable to rotavirus gastroenteritis.

The study, published in The Lancet last week (5 April), enrolled more than 15,000 infants aged 6–13 weeks. Each was randomly assigned either two doses of Rotarix — an oral live attenuated rotavirus vaccine — or a placebo, at around two and four months, and followed up for two years.

Children from Argentina, Brazil, Chile, Colombia, Dominican Republic, Honduras, Mexico, Nicaragua, Panama, and Venezuela were included in the trial.

The vaccine was found to prevent around 80 per cent of severe rotavirus gastroenteritis cases and 83 per cent of hospital admissions for the illness over the two years.

Previous studies using the same vaccine and a second, RotaTeq, have shown protection during the first year of life (see Double vaccine victory over rotavirus).

But in Latin America, where rotavirus causes 15,000 deaths a year, the peak incidence of rotavirus gastroenteritis occurs between 6 and 24 months of age — meaning protection is needed during at least the first two years of life.

"The results are likely to be similar in other developing countries with a middle-income population and cultural background similar to these Latin American countries," Miguel O'Ryan, one of the researchers from the University of Chile, told SciDev.Net.

But, O'Ryan says, "similar studies in countries with severe malnutrition and precarious sanitation conditions are needed to complement these results".

The vaccine is derived from the most commonly circulating strain of rotavirus, and also offered good protection against some other strains across the two-year period. But it only offered low protection against one rarer strain, which the authors say needs more investigation.

In an accompanying comment, Keith Grimwood and Carl Kirkwood, from the Queensland Paediatric Infectious Disease Laboratory in Australia, write that the results of trials in Africa and Asia, where there is more diversity in rotavirus strains and 413,000 rotavirus deaths occur every year, will be important in evaluating the effectiveness of this vaccine.

Link to full paper in The Lancet*

Link to comment in The Lancet*

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The Lancet 371, 1181 (2008)