Stopping rotavirus before it hits

WASHINGTON — A vaccine against rotavirus has provided potent protection in its first year of widespread use.

Reporting October 25 at a meeting of microbiologists and infectious disease researchers, scientists offered up several studies demonstrating that the oral vaccine has brought about a sharp decline in rotavirus infections in the United States during 2007–2008.

Rotavirus kills roughly 500,000 people annually, most of them children in developing countries.

“This is a remarkable success,” says Jay Lieberman, leader of one study and the Cypress, Calif.-based medical director for infectious diseases at Quest Diagnostics, a clinical laboratory company.

Lieberman and his colleagues used a Quest database to check for new trends in rotavirus infections after the vaccine’s approval in 2006. The peak season for rotavirus infection in the United States is December to June. In the three seasons before the vaccine was put into common use, one in four Quest lab tests for rotavirus had come back positive. In the infectious season spanning 2007 to 2008, that rate dropped to less than one in 12 tests, Lieberman says. The researchers compared more than 15,000 tests in the post-vaccine period with over 60,000 tests conducted in the previous three years.

The Centers for Disease Control and Prevention in Atlanta assessed data from a national reporting system used by laboratories across the country and reached a similar conclusion. CDC medical epidemiologist Margaret Cortese reports at the same meeting that the 2007–2008 cases of rotavirus declined by at least 60 percent from the average seen over the five preceding years.

Typically, the United States records 20 to 60 deaths from rotavirus annually, but mortality data are not yet available for the post-vaccine season, she says.

The approved regimen for the rotavirus vaccine is three doses, one each given at two, four and six months of age. Doctors decide individually whether to add the rotavirus vaccine to children’s vaccination schedule, and so U.S. coverage isn’t 100 percent yet, these researchers say.

The vaccine uses portions of bovine and human rotavirus proteins to engender immunity in babies. It was devised by H. Fred Clark and his colleagues at the University of Pennsylvania in Philadelphia, starting in the 1980s and perfected in the years since that time. It’s now manufactured by Merck & Co. Inc. at its West Point, Pa., operation.

Clark says that the new nationwide studies echo the results that he and his colleagues have found in a multiyear tracking study of a Philadelphia-area population, which has seen rotavirus cases drop from hundreds per year to only 12 in the 2007–2008 season. He is particularly encouraged by the near-total lack of side effects from the vaccine in the general population, he says.

Merck itself also presented a study on the vaccine’s effectiveness, using insurance company data to compare more than 45,000 infants. Roughly half of the infants had received the vaccine. Christopher Mast, an epidemiologist at Merck’s North Wales, Pa., office, reports dramatically fewer hospitalizations and doctor visits attributable to rotavirus infection among the vaccine recipients compared with the non-recipients.

The studies were presented in Washington, D.C., at a combined meeting of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy.

The findings set the stage for a worldwide assault on this diarrhea-causing virus. Merck is distributing the vaccine, called RotaTeq, in Latin America and the Caribbean as part of public health programs and is conducting clinical trials to test its effects in Africa and Asia.

GlaxoSmithKline is also marketing a new rotavirus vaccine, dubbed Rotarix. The oral, two-dose vaccine gained U.S. regulatory approval earlier this year.