Intussusception following rotavirus vaccine administration: Post-marketing surveillance in the National Immunization Program in Australia

IntroductionIn Australia, post-marketing surveillance for intussusception following vaccination commenced with funding of RotaTeq® and Rotarix® vaccines under the National Immunization Program (NIP) in July 2007.MethodsTwo active surveillance mechanisms (hospital-based case ascertainment and monthly reports from paediatricians) identified intussusception cases between 1st July 2007 and 31st December 2008 in four states. Linkage to vaccination records identified cases occurring within 1–7 and 1–21 days of rotavirus vaccination. Expected cases within the post-vaccination windows were calculated by applying rates of intussusception from national hospitalisation data over 6 years (mid-2000 to mid-2006), by age and state, to numbers vaccinated (by dose) according to the Australian Childhood Immunization Register.ResultsCombining exposure windows associated with all doses of rotavirus vaccine from 1 to 9 months of age, there was no evidence of an increased risk of intussusception following vaccination for either vaccine. However, in infants 1 to <3 months of age, there was suggestive evidence of excess intussusception cases 1–7 and 1–21 days following dose 1 (1–7 days: RotaTeq® relative risk (RR) = 5.3, 95% confidence interval [CI] 1.1,15.4; Rotarix® RR 3.5, 95% CI 0.7,10.1; 1–21 days: RotaTeq® RR 3.5, 95% CI 1.3, 7.6; Rotarix®RR 1.5, 95% CI 0.4, 3.9). There was no evidence that clinical outcome of intussusception occurring within 21 days of rotavirus vaccination differed from that in cases occurring later post-vaccination.ConclusionAlthough we found no overall increase in intussusception following receipt of rotavirus vaccine, there was some evidence of an elevated risk following the first dose of both vaccines. Larger population-based studies using linked databases are required to provide more definitive evidence.