A vaccine can protect babies from rotavirus, the most common cause of severe diarrhea in infants.

Rotavirus accounts for up to 272,000 emergency room trips and 70,000 hospital stays a year, the CDC says.

"Almost every child has had rotavirus at least once by the time they reach 5 years old," says Penelope Dennehy, M.D., a Providence, R.I., pediatrician who specializes in rotavirus infection. Dr. Dennehy serves on the American Academy of Pediatrics' infectious diseases committee.

Very contagious
The highly contagious virus can live a long time outside the body. It lurks in the stool of an infected child before, during, and after symptoms show up. If that child skips hand-washing after using the bathroom, another child can pick up the virus. This happens when the second child touches the same objects and puts his hand to his mouth.

"It initially starts off with fever, then the child starts vomiting and will vomit for a couple of days," says Dr. Dennehy. "From there, they go on to develop the diarrhea. They get dehydrated very easily because of that."

The virus can infect children more than once. The first case tends to be the worst. After each case, kids are less and less likely to come down with a new infection.

The FDA approved the vaccine, RotaTeq, in 2006. The CDC recommends it for babies up to 6 months old. It's given by mouth as a liquid. Infants get three doses, at 2 months, 4 months, and 6 months. The vaccine is not meant for older kids.

Effective vaccine
Doctors tested RotaTeq on more than 70,000 children, the CDC says. Half got the real vaccine and half got a sham dose. When doctors compared the groups, this is what they found in kids who got the real vaccine:

• 74 percent fewer cases of rotavirus associated diarrhea
• 98 percent fewer severe cases of diarrhea
• 96 percent fewer hospital stays due to rotavirus

In 1998, the FDA approved a different rotavirus vaccine. That vaccine was dropped after being linked to cases of intussusception, a rare, life-threatening blockage or twisting of the bowels. Studies of RotaTeq before its release, found no such problem. The FDA said in February 2007, however, that after doctors began to use RotaTeq, it received 28 reports of the bowel problem. That could be a coincidence, the FDA says, because the problem can occur on its own. So far the number of cases reported is consistent with the number of cases expected based on children who are unvaccinated. However, the FDA has asked doctors and parents to watch for the problem. Without the vaccine, it's tough to avoid rotavirus because it's passed so easily. But remember, this vaccine only shields kids from rotavirus. You can help protect them from other viruses by making sure they—and you—wash hands after using the bathroom and before eating. Wash your hands after changing diapers, too.

Make sure you clean affected surfaces quickly with household chlorine bleach-based products.

Wash soiled clothing as soon as possible.