Two research studies published yesterday in the New England Journal of Medicine report an elevated risk of intussusception, a rare but dangerous bowel obstruction in infants, after rotavirus vaccination.
Practitioners have been concerned about intussusception risk since 1999, when the manufacturer of a tetravalent rotavirus vaccine withdrew it after it was shown to be associated with between 1 and 2 excess cases of intussusception per 10,000 infants vaccinated, Family Practice News reports. The first clinical studies of two newer vaccines, a pentavalent introduced in 2006 and a monovalent, introduced in 2008, showed no such excess intussusception risk, but more recent studies have indicated excess risk associated with these newer vaccines as well, though to a lesser degree. The first New England Journal of Medicine study reports evidence for a slight but statistically significant increase in intussusception risk associated with use of Merck’s pentavalent vaccine, RV5 (RotaTeq). A team led by Katherine Yih, Ph.D., of Harvard Medical School and the Harvard Pilgrim Health Care Institute, Boston, looked at data from more than 1.2 million doses of RV5. The Food and Drug Administration (FDA) sponsored the study, and data were derived from health plans included in the FDA’s Mini-Sentinel surveillance program. Dr. Yih and colleagues found an excess risk of 1.5 cases per 100,000 within 21 days after the first dose (95% confidence interval, 0.2-3.2), with no further increases in risk seen after the second or third dose, according to Family Practice News. Yih’s team also looked at data from 103,098 doses of a monovalent vaccine, GlaxoSmithKline’s RV1 (Rotarix). Increased risk was seen after the second dose, though the researchers note that this study was insufficiently powered to demonstrate a statistically significant risk in association with the monovalent vaccine.
For the second new study, a research team led by Eric Weintraub of the Centers for Disease Control and Prevention (CDC) looked at data from 207,955 doses of the monovalent vaccine, identifying intussusception cases recorded within seven days after a first or second dose. They found 5.3 excess cases over expected background rates per 100,000 infants vaccinated with two doses, according to Family Practice News. Weintraub and his colleagues found no increased risk associated with the pentavalent vaccine, for which they had data on 1,301,810 doses.
According to the CDC, rotavirus is the leading cause of severe diarrhea in infants and young children worldwide, and annually, it is the cause of more than a half a million deaths in children younger than five.