More Intussusception Hospitalizations in California After Rotavirus Vaccine Introduction

The risk of intussusception hospitalizations in infants in California has risen since the introduction of rotavirus vaccines in 2006 and 2008, according to researchers.

The risk of intussusception hospitalizations in infants in California has risen since the introduction of rotavirus vaccines in 2006 and 2008, according to researchers.

"We identified a small, but demonstrable increased risk in intussusception hospitalizations in California children less than 1 year of age, compared to the preceding period 2000-2005," Dr. Despina G. Contopoulos-Ioannidis, of Stanford University School of Medicine in Stanford, California, told Reuters Health by email.

In a March 19 online paper in the Pediatric Infectious Disease Journal, Dr. Contopoulos-Ioannidis and colleagues note that a previous vaccine, the RotaShield was introduced in the U.S. in 1998 and withdrawn in 1999 because of an association with increased risk for intussusception.

Two newer rotavirus vaccines were subsequently licensed in the U.S. in 2006 (RotaTeq) and 2008 (Rotarix). They have since been associated with a small increase in intussusception risk in active vaccine surveillance studies.

The team examined California data on hospital discharges of infants with intussusception diagnoses. They covered the periods 1985-1997, when only one live enteric virus vaccine (oral poliovirus vaccine) was recommended, 2000-2005, when no recommendation existed for any live enteric virus vaccine, and 2006-2010, following introduction of the new vaccines.

In the latter period, the investigators wrote, "We detected a small, but demonstrable increase in the intussusception risk compared to the preceding period 2000-2005. This finding was consistent across different statistical analyses."

An increase in the incidence rate slopes occurred in 2006-2010 versus 2000-2005 with a 3.2 excess of intussusception cases per 100,000 births per year. This was of borderline significance. A significant 10% increase also occurred in the mean incidence rate of intussusception hospitalizations in 2006-2010 versus 2000-2005.

The 6-14 weeks age subgroup had the highest intussusception incidence rate in 2006-2010.

Overall, the investigators wrote, "The increased population level risk we detected is consistent with the small increased intussusception risk of ~1-5 excess intussusception cases per 100,000 vaccinated infants recently seen in two active vaccine surveillance projects in the U.S."

Dr. Contopoulos-Ioannidis added, "Physicians should be aware of this small increased intussusception risk after the new rotavirus vaccines and promptly consider this diagnosis if consistent signs and symptoms are present. Moreover, surveillance studies of intussusception risk post rotavirus vaccinations should be continued."

However, the researchers also observed, "We do not know the vaccination coverage rate specifically for the infants in our cohort," and the immunization differences between the periods in question were based ecologic assumptions.

Commenting on the findings by email, Dr. Joseph Zickafoose, of the University of Michigan, Ann Arbor, told Reuters Health, "This seems to be a very well-done study. The results are a little surprising to me since my co-authors and I did a very similar study using nationwide data and found no increase in rates of intussusception after 2006." (Here:

"But," added Dr. Zickafoose, "that is why it is important to do multiple studies in multiple places. It is possible that their findings are related to the re-introduction of rotavirus vaccine, but as they point out, they can't say how many of the children with intussusception were immunized against rotavirus."

He added, "They very responsibly point out some possible other explanations. One thing they did not explore is whether the trend could be related to increased rates of other gastrointestinal illnesses during the later years. That would be very difficult to assess though."

The authors reported no external funding or disclosures.


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