FRIDAY, Jan. 13 (HealthDay News) -- Updated vaccines for rotavirus -- once the leading cause of gastrointestinal illness among U.S. children -- do not appear to increase the risk of potentially deadly side effects, a new study finds.

The original rotavirus vaccine was taken off the market in 1999 after it was associated with severe bowel obstruction called intussusception.

The two updated versions of the vaccine were reintroduced in 2006 and 2008, and more than 70 percent of infants in the United States have been vaccinated against rotavirus, which causes abdominal pain, severe diarrhea and vomiting.

Hospitalization is required for many infants and young children infected with rotavirus.

In this study, a team at the University of Michigan C.S. Mott Children's Hospital examined national data in order to compare intussusception rates among children younger than age 1 before and after vaccine reintroduction.

The investigators expected to find 36 intussusception-related hospitalizations per 100,000 children in 2009, but found that the rate was only 33.3 cases per 100,000. This suggests that it's very unlikely that the reintroduced vaccines led to any additional cases of intussusception, the researchers said.

The study was published online Jan. 2 in the journal Archives of Pediatrics and Adolescent Medicine.

"We always need to carefully weigh the risks and benefits of childhood vaccines. Fortunately, our results suggest that rotavirus vaccines have not increased the rate of intussusception in the U.S.," lead author Dr. Joseph Zickafoose, a pediatrician and research fellow with the Child Health Evaluation and Research Unit, said in a University of Michigan news release.

"We hope that our study provides information that will continue to reassure parents that the benefits of rotavirus vaccine outweigh the risks," he added.

More information

The U.S. Centers for Disease Control and Prevention has more about rotavirus.