Rotavirus rates fell in adults, too, after vaccine

(Reuters Health) - Fewer older children and adults were hospitalized for severe diarrhea once the U.S. started vaccinating babies against rotavirus in 2006, according to a new study.

Rotavirus is one cause of the "stomach flu," or gastroenteritis, and introduction of the rotavirus vaccine has already been tied to a drop in related hospitalizations among preschoolers. But whether vaccinating babies would also confer protection for older people was unclear, researchers said.

"This study confirms the benefits of the rotavirus vaccine program, but it also shows there's an unexpected benefit to the population at large," Ben Lopman, who worked on the study at the U.S. Centers for Disease Control and Prevention, said.

"This is one example of what we call herd immunity," he told Reuters Health.

"By vaccinating young children you prevent them from getting sick, but you also prevent them from transmitting (rotavirus) to their siblings and their parents."

The initial rotavirus vaccine was introduced in the U.S. in 1998 and pulled the following year due to concerns it might cause blocked bowels in babies.

Newer versions, which are given orally, became routine in 2007. Pre- and post-release testing of those vaccines has not shown those same side effects (see Reuters Health story of January 5, 2012 here:reut.rs/AAe8bT).

For their study, the CDC researchers compared data on a nationally-representative sample of hospital stays by children and adults diagnosed with rotavirus or unspecified gastroenteritis in 2000-2006 and 2008-2010.

Rotavirus testing is rarely performed in adults, they noted, so many more unspecified gastroenteritis cases were included.

As previous studies have shown, rotavirus rates among young children dropped after the start of vaccination; there were 80 percent fewer discharges for rotavirus among kids under five in the post-vaccine study years than in pre-vaccine years.