Intussusception among infants given an oral rotavirus vaccine.

Background: Intussusception is a form of intestinal obstruction in which a segment of the bowel prolapses into a more distal segment. Our investigatio n began on May 27, 1999, after nine cases of infants who had intussusceptio n after receiving the tetravalent rhesus-human reassortant rotavirus vaccin e (RRV-TV) were reported to the Vaccine Adverse Event Reporting System. Methods: In 19 states, we assessed the potential association between RRV-TV and intussusception among infants at least 1 but less than 12 months old. Infants hospitalized between November 1, 1998, and June 30, 1999, were iden tified by systematic reviews of medical and radiologic records. Each infant with intussusception was matched according to age with four healthy contro l infants who had been born at the same hospital as the infant with intussu sception. Information on vaccinations was verified by the provider. Results: Data were analyzed for 429 infants with intussusception and 1763 m atched controls in a case-control analysis as well as for 432 infants with intussusception in a case-series analysis. Seventy-four of the 429 infants with intussusception (17.2 percent) and 226 of the 1763 controls (12.8 perc ent) had received RRV-TV (P=0.02). An increased risk of intussusception 3 t o 14 days after the first dose of RRV-TV was found in the case-control anal ysis (adjusted odds ratio, 21.7; 95 percent confidence interval, 9.6 to 48. 9). In the case-series analysis, the incidence-rate ratio was 29.4 (95 perc ent confidence interval, 16.1 to 53.6) for days 3 through 14 after a first dose. There was also an increase in the risk of intussusception after the s econd dose of the vaccine, but it was smaller than the increase in risk aft er the first dose. Assuming full implementation of a national program of va ccination with RRV-TV, we estimated that 1 case of intussusception attribut able to the vaccine would occur for every 4670 to 9474 infants vaccinated. Conclusions: The strong association between vaccination with RRV-TV and int ussusception among otherwise healthy infants supports the existence of a ca usal relation. Rotavirus vaccines with an improved safety profile are urgen tly needed. (N Engl J Med 2001;344:564-72.) Copyright (C) 2001 Massachusett s Medical Society.