Trends in Hospitalizations for Intussusception in California in Relationship to the Introduction of New Rotavirus Vaccines, 1985-2010

Background: The new rotavirus vaccines RV5 and RV1 have been associated with small increase in intussusception risk in active vaccine surveillance studies. It is unclear what the impact might be on the overall trends of intussusception hospitalizations at a large population basis. Methods: We conducted an ecological study of hospital discharges of infants with intussusception discharge diagnosis using the California Office of Statewide Health Planning and Development database (1985-2010). We measured incidence rates (IR) of intussusception hospitalizations per 100,000 births within 3 periods (1985-1997; 2000-2005; 2006-2010) related to past, pre-introduction and post-introduction of the new rotavirus vaccines. We estimated slopes of yearly IRs within each period, changes in slopes between periods and IR ratios (IR) of the mean IRs between periods. We did subgroup analyses for 5 age-subgroups. We also analyzed intussusception hospitalizations of infants who also had a surgical repair and/or radiologic reduction procedure code (restricted cohort). Results: We identified 6241 intussusception hospitalizations; 4696 also had pertinent procedure codes. There was an upward trend in yearly IRs during 2006-2010 (+2 excess cases per 100,000 births per year; P = 0.023); the change in slopes between 2006-2010 and 2000-2005 was +3.2 excess cases per 100,000 births per year (P = 0.052), and the IR in 2006-2010 was 10% higher than in 2000-2005 (IR: 1.10; 95% confidence intervals: 1.01-1.19). The IR in 2006-2010 versus 2000-2005 for the 6-14 weeks agesubgroup was 1.90 (95% confidence intervals: 1.33-2.74). In the restricted cohort, trends were similar, though not nominally significant. Conclusions: We documented at a population-level a small increased risk in intussusception hospitalizations post-introduction of the new rotavirus vaccines.