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.
From the *Epidemiology, OptumInsight, Waltham, MA; †Department of Epidemiology, Merck Research Laboratories, North Wales, PA; ‡Department of Epidemiology, Harvard School of Public Health, Boston, MA; and §Division of Pharmacoepidemiology, Harvard Medical School/Brigham and Women's Hospital, Boston, MA.
Accepted for publication November 14, 2011.
Supported by a research contract between OptumInsight (formerly Ingenix) and Merck & Co., Inc. The contract granted OptumInsight oversight of the study conduct, reporting and interpretation as well as journal submission and final wording of any resulting manuscripts.
The authors have no other funding or conflicts of interest to disclose.
Address for correspondence: Jeanne Loughlin, MS, Epidemiology, OptumInsight, 950 Winter St, Suite 3800, Waltham, MA 02451. E-mail: Jeanne.Loughlin@optum.com.