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Investigators from 2 independent groups conducted postmarketing surveillance studies to determine the risk of intussusception among US infants after vaccination with the rotavirus vaccines, RotaTeq (RV5) and Rotarix (RV1). One study was initiated by the FDA as part of the Post-Licensure Rapid Immunization Safety Monitoring (PRISM) program, which utilized clinic data from 3 large insurance groups (FDA study). The other study was initiated by the CDC as part of the Vaccine Safety Datalink (VSD) program, which utilized electronic data from 6 integrated health care organizations (CDC study).

The FDA study included infants 5.0 to 36.9 weeks of age enrolled in the PRISM-participating health plans from 2004 through mid-2011. Vaccine exposures were identified using CPT codes. Potential intussusception cases were identified using ICD-9 codes from the inpatient or emergency department (ED) setting. Only cases of intussusception that occurred within 42 days after vaccination were included. The number of cases of intussusception in 2 intervals (days 1–7 and 1–21 after vaccination) were compared to the control interval (days 22–42) in the primary analysis. The secondary analysis used a cohort design that included exposed (days 1–21) and unexposed periods (day of vaccination and days 22–42). Investigators calculated the attributable risk as the number of excess cases of intussusception (considering published age-specific background rates) per 100,000 vaccine doses administered.

Analyses included 507,874 first doses and 1,277,556 total doses of RV5, and 53,638 first doses and 103,098 total doses of RV1. After the first dose of RV5, the attributable risk of intussusception per 100,000 doses was 1.1 (95% CI, 0.3–2.7) for the 7-day risk interval, and 1.5 (95% CI, 0.2–3.2) for the 21-day risk interval. In the secondary analysis, the attributable risk was 1.2 (95% CI, 0.2–3.2) for the exposed period. No increase in risk was seen after dose 2 or 3. For RV1, there was only 1 case of intussusception in the risk interval, and no cases in the control interval. In the primary analysis, the attributable risk was not significant for either dose. In the secondary analysis, the attributable risk was 7.3 (95% CI, 0.8–22.5) after dose 2.

The CDC study included infants 4 to 34 weeks of age. Potential intussusception cases within 7 days of RV1 were identified by review of ICD-9 codes from hospital and ED visits between 2008 and 2013. The relative risk (RR) of intussusception among infants receiving RV1 was calculated by dividing the number of observed cases by the number of expected cases based on historical background rates. This RR was compared to an updated RR...

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