Background: To estimate the incidence of intussusception among infants treated in inpatient and emergency department settings during the period preceding the US launch of second-generation rotavirus vaccines.
Methods: From a large US health insurance claims database, we sampled 100,000 infants aged 1 to 3 months at first diphtheria-tetanus-acellular pertussis vaccination between 2001 and 2005. Potential intussusception cases were identified on the basis of claims and were confirmed by medical record review. Incidence rates (IRs) and 95% confidence intervals (CIs) were estimated based on follow-up from first diphtheria-tetanus-acellular pertussis dose to up to 1 year of age, and within 21, 30, and 60 days after each dose.
Results: The IR of intussusception in the first year of life was 0.33/1000 person-years based on 22 confirmed cases (95% CI: 0.21–0.50/1000 person-years). The age-specific incidence peaked among infants aged 5 months (IR: 0.82/1000 person-years; 95% CI: 0.30–1.78/1000 person-years). During the 21, 30, and 60 days following any dose, the incidence per 1000 person-years was 0.27, 0.24, and 0.33, respectively.
Conclusion: The rates described in this study can serve as a benchmark for comparison with incidences observed after the introduction of the second-generation rotavirus vaccines.