Merck's rotavirus vaccine 98% effective, study says

By Angela McDaniels

Seattle, Jan. 4 - Merck & Co. Inc. said that in a new study of 68,038 infants, the company's investigational vaccine Rotateq prevented 98% of severe cases of rotavirus gastroenteritis.

The trial was a double-blind, randomized, placebo-controlled study and one of the largest vaccine clinical trials ever conducted, the company said. It began in 2001 and enrolled infants between six and 12 weeks of age in the United States, Belgium, Costa Rica, Finland, Germany, Guatemala, Italy, Jamaica, Mexico, Sweden and Taiwan. Infants were randomly assigned to receive three doses of vaccine or placebo, given four to 10 weeks apart.

Mercke said that among the 5,673 infants included in an efficacy sub-study, Rotateq demonstrated 98% efficacy against severe rotavirus gastroenteritis and 74% efficacy against rotavirus gastroenteritis of any severity caused by serotypes targeted by the vaccine (G1, G2, G3, G4) as compared to placebo through the first full rotavirus season after vaccination.

Among the infants included in the large scale study, Rotateq reduced hospitalizations for rotavirus gastroenteritis caused by serotypes targeted by the vaccine by 96% and reduced emergency room visits by 94%.

Because intussusception - an intestinal blockage caused by the bowels folding in on themselves - was associated with a previously licensed rotavirus vaccine made by another manufacturer, one of the primary goals of the trial was to evaluate the safety of Rotateq with respect to intussusception among vaccine and placebo recipients.

There were six cases of intussusception in the vaccine group and five in the placebo group during the six-week period following any dose, the company said. Within one year after the first dose, there were 12 cases of intussusception in the vaccine group and 15 in the placebo group.

Rotateq was generally well-tolerated when compared to placebo.

The results were published in this week's New England Journal of Medicine.

Rotavirus is the most common cause of severe dehydrating diarrhea in infants and young children, Merck said. Among children under five, it is responsible for an estimated two million hospitalizations, 500,000 deaths and more than 25 million clinic visits worldwide each year.

Rotateq is an oral, liquid vaccine that contains five rotavirus strains: G1, G2, G3, G4 and P1. These serotypes cause most rotavirus disease worldwide.

Merck said it has submitted an application for licensure of Rotateq in more than 50 countries, including the United States and the European Union, and plans to initiate clinical studies this year to evaluate the use of Rotateq in the developing world.

Merck is a pharmaceutical company based in Whitehouse Station, N.J., that develops vaccines and medicines in more than 20 therapeutic categories.

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