Intussusception, rotavirus diarrhea, and rotavirus vaccine use among children in New York State

Objective. To describe epidemiologic features of intussusception and rotavi rus diarrhea in New York, to examine the baseline incidence and trends over time, and to ascertain whether an excess of cases occurred in the 9 months of vaccination with the newly licensed rotavirus vaccine. Methods. Hospital discharge data from 1989 through 1998 were reviewed for c hildren (<1 year old) whose primary or secondary diagnosis was coded as int ussusception or rotavirus diarrhea. Characteristics of patients admitted fo r intussusception and rotavirus diarrhea were compared, and trends over tim e were examined. For a subset of patients, medical records and vaccine hist ories for intussusception hospitalizations from October 1998 through June 1 999 were analyzed. The number of intussusception cases attributable to rota virus vaccine was calculated based on the penetration of the vaccine (21%) and a range of excess risks of intussusception among vaccinated children as estimated by the National Immunization Program (NIP). Results. From 1989 through 1998, 1450 intussusception-associated hospitaliz ations were reported in children <1 year old (average annual incidence 5.4/ 10000). Among these children, 47% were treated medically and 53% had surger y, with 9% needing surgical resection. The incidence of intussusception dec lined over time from 6.1 per 10000 in 1989 to 3.9 per 10000 in 1998. Intuss usception hospitalizations occurred throughout the year, whereas rotavirus- associated hospitalizations peaked from February to April. Of 20 patients w ith intussusception whose hospitalization charts were reviewed, 5 had recei ved rotavirus vaccine. All 5 were hospitalized after their first dose of va ccine, were admitted before 7 months of age, were white, and had private in surance. A total of 81 cases of intussusception occurred during the 9-month period of rotavirus vaccination, compared with 78 during the same period i n the prevaccination year. The number of excess intussusception cases obser ved (n = 3) was lower than expected using the NIP estimate of excess risk ( 1.8) among rotavirus vaccinated children (n = 12) but not significantly dif ferent from the risks identified in the NIP cohort studies (1 in 12 000). Conclusion. Our data suggest that in New York the rate of intussusception h as declined, and approximately 1 child in 2600 develops intussusception bef ore 1 year of age. The different seasonality between intussusception and ro tavirus-related hospitalizations suggests that if any causal association ex ists, it must be small. Unlike other studies, analysis of New York hospital ized discharge data failed to show an appreciable increase in the incidence of intussusception after introduction of the rotavirus vaccine.