A rotavirus vaccine approved in 2006 is having a significant impact in the United States, delaying the onset of the rotavirus season by three months and reducing its severity by about half, federal officials said Wednesday.
The incidence of rotavirus activity during the first months of 2008 was the lowest it has been since the federal Centers for Disease Control and Prevention began monitoring the illness 15 years ago, researchers from the agency reported in the CDC’s Morbidity and Mortality Weekly Report.
The highly contagious virus is the leading cause of severe vomiting and diarrhea in infants and young children in the United States and around the world. Each year in this country, it causes more than 400,000 physician office visits, as many as 272,000 emergency-room visits, up to 70,000 hospitalizations and 20 to 60 deaths. Worldwide, about 500,000 children die from the infection each year.
The RotaTeq vaccine has been shown to prevent 74% of all rotavirus infections, 98% of severe infections and about 96% of hospitalizations. The CDC recommends that all infants receive their first dose of the vaccine by 12 weeks of age and all three required doses by 32 weeks.
No good data exist on the number of children who have been vaccinated, but studies at selected sites suggest that about half of 12-week-olds have received one shot and that about a third of 13-month-olds have received all three doses.
The decline in new cases appears “greater than expected based on the protective effects of the vaccine alone,” Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases, said in a statement. She speculated that vaccination was helping to reduce the spread of the virus to unvaccinated individuals.
No agency tracks all cases of rotavirus in the United States. The new data come from the New Vaccine Surveillance Network, which tracks the virus in three typical counties, and the National Respiratory and Enteric Virus Surveillance System, a voluntary network of U.S. laboratories that test for the virus in samples provided by physicians.
For the last 15 years, the rotavirus season typically has begun in mid-November. This past winter, according to the report, it began in late February. The number of tests performed for rotavirus during the season was, on average, 37% lower than the number in previous years, and the number of positive tests was 78.5% lower.
In the three sentinel counties, the percentage of stool samples testing positive for rotavirus in children under 3 was 51% in 2006, 54% in 2007 and 6% in 2008.