By Lisa Rapaport

(Reuters Health) – More than a decade after the rotavirus vaccine was added to the roster of routine shots recommended for all infants in the U.S., vaccination is still reducing hospitalizations for severe infections, researchers say.

Researchers tracked hospitalizations for children under age 5 from 2009 to 2016, a period following the debut of two new rotavirus vaccines in the U.S. They found that, compared to unvaccinated kids, children who got just one dose of the rotavirus were 82% less likely to be admitted to the hospital with a rotavirus infection and 75% less likely to have an emergency department visit because of the disease.

Kids who weren’t vaccinated had severe rotavirus infections four times more often than children who got the vaccines, the study also found.

“Since the virus still exists throughout the environment and is very easily transmitted, any hope of a child permanently avoiding a rotavirus infection is unlikely,” said Daniel Payne, lead author of the study and a researcher at the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta.

“Eventually, all unvaccinated children will be exposed to infection, and some of these infections will be severe,” Payne said by email. “Our study indicates that rotavirus vaccines significantly prevent hospitalizations and severe infections when young children are infected.”

Rotavirus can cause severe watery diarrhea, vomiting, fever and abdominal pain. Some children can become extremely dehydrated, requiring hospitalization. If untreated, the condition can prove fatal, but most children vaccinated against rotavirus will be spared severe effects, according to the CDC.

The virus spreads in stool and can be easily passed from one child to the next when they share toys or food, particularly while children are still in diapers.

An older vaccine to prevent the virus, RotaShield, was introduced and withdrawn in the U.S. in the late 1990s after it was linked to intussusception in infants. Intussusception is a serious condition that develops when the intestines become tangled and obstructed; it can be fatal if not quickly treated.

Two new vaccines, RotaTeq and Rotarix, were approved for sale in the U.S. in 2006 and 2008, respectively. So far, the potential for intussusception appears extremely rare with these vaccines.

Both vaccines are given to infants in oral drops in multiple doses over several months; RotaTeq is administered three times, while Rotarix is given twice.

In the study, there was no meaningful difference in outcomes based on whether infants got RotaTeq or Rotarix.

Across the seven-year study period, an average of 87% of kids in the study population had received at least one vaccine dose.

To assess the effectiveness of these vaccines, researchers examined data from seven emergency rooms across the U.S., including a total of 1,193 kids who had laboratory-confirmed rotavirus and 9,620 kids who did not have the virus. All were treated for acute gastroenteritis – defined as more than three episodes of diarrhea or more than one of vomiting within the previous 24 hours.

In addition to protecting against hospital admissions, the vaccine was associated with less-severe symptoms. Among kids with rotavirus, 17% of those who were not vaccinated had very severe symptoms compared with 4.6% of kids who had been vaccinated.

The results suggest that the rotavirus vaccine should continue to be recommended as a routine childhood vaccination, researchers conclude in JAMA Network Open.

“Both rotavirus vaccines currently licensed in the U.S. continue to be effective,” Payne said.

“Our real-world study of rotavirus vaccine performance confirmed that these vaccines are significantly reducing the clinical severity of rotavirus infections in childhood.”

SOURCE: JAMA Network Open, online September 27, 2019.