Within six years of the introduction of the rotavirus vaccine, hospitalizations for the diarrheal illness had dropped by 94 percent and hospitalizations for overall gastrointestinal illnesses were cut in half. Those are the findings of CDC-funded research published in JAMA today.
The first vaccine, RotaTeq by Merck, was introduced in 2006, followed by Rotarix by GlaxoSmithKline in 2008, so there were not exactly major changes to sanitation or a sudden improvement in medical care during that time of the vaccines’ introduction. In fact, the decline in rotavirus cases may be underestimated because so few of the gastrointestinal hospitalizations included testing for it, meaning many cases were likely missed.
“Yet again we are seeing just how effective our immunization programs are at reducing the risk of illness in vulnerable populations,” said Clay Jones, a neonatal hospitalist at Newton–Wellesley Hospital in Newton, Massachusetts, who was not involved in the study. “This study should inspire further efforts to improve the rates of rotavirus immunization in young children.”
Rotavirus is a gastrointestinal illness that typically causes severe vomiting and diarrhea for about a week, putting children at high risk for dehydration. In the U.S., where resources are usually abundant, children do not usually die from the disease. The World Health Organization, however, estimated in 2004, before the vaccine was introduced, that half million children a year died from the disease.
“Rotavirus kills hundreds of thousands of children under the age of five every year, but we are lucky to live in a country where fatal outcomes are a fraction of those seen around the world,” Jones said. “But it is still a terrible illness which brings with it a great burden on society.”
The track record for the rotavirus vaccine has already been strong, and some past research has even found strong evidence for the effect of herd immunity in preventing the illness even among children who had not received the vaccine. But this study is among the largest to look at the overall effect of the vaccine’s introduction across the U.S. Researchers at the CDC analyzed de-identified records of hospital admissions in an inpatient database for the 26 states who reported their hospital discharge data every year from 2000 through 2012.
Among more than 1.2 million cases of gastrointestinal illnesses in children under 5 during those years, about 17 percent were specifically diagnosed with rotavirus. But since many children with GI infections do not receive testing for rotavirus, the researchers compared the pre-vaccine cases (2000-2006) with the post-vaccine cases (2008-2012) for both rotavirus and for general GI hospitalizations.
The drop in the years after the vaccine’s introduction is dramatic: rotavirus cases went from 16 per 10,000 children in the pre-vaccine era to 5-6 cases per 10,000 in the couple years after the vaccine to 1 case per 10,000 children a year in 2012, the year when vaccine coverage was the highest. The decline ranged from 63 to 94 percent lower than the rate before 2007.
Similarly, hospitalizations for any kind of GI infection went from 76 cases per 10,000 children before the vaccine to 34 cases per 10,000 children in 2012. The cases dropped by nearly a third in 2008, the year after the vaccine had been out for at least a full year, and hit their lowest in 2012, when GI hospitalizations were 55 percent lower than they were in the pre-vaccine first half of the 2000s.
“Pediatric healthcare professionals already tend to shout from the rooftops about vaccine safety and efficacy,” Jones said. “This study isn’t surprising given what we already know, but it’s still great news and something which needs to be shared with vaccine hesitant caregivers.”
The most serious risk of the rotavirus vaccine is a bowel obstruction disorder called intussusception, estimated to occur as often as 1 in 20,000 doses of the vaccine. You can find here an in-depth examination of the risks and benefits of the vaccine with regards to intussusception, including typical treatments and outcomes for both rotavirus and the bowel disorder.