Effect of rotavirus vaccination programme on trends in admission of infants to hospital for intussusception

Background Studies have reported a temporal association between a first dos e of rotavirus vaccine (Rotashield) and infant intussusception. We investig ated the effect of Rotashield vaccination use on intussusception admissions in ten US states. Methods We analysed electronic databases containing 100% hospital discharge records for 1993-99 from ten US states, where an estimated 28% of the birt h cohort had received Rotashield (based on manufacturer's net sales data). We examined records of infants admitted to hospital (<365 days old) with an y mention of intussusception (international Classification of Diseases, nin th revision. clinical modification code 560.0). Excess admissions for intus susception during the period of Rotashield availability (October 1998 to Ju ne 1999) were estimated by direct comparison with the corresponding period of October 1997 to June 1998 (before Rotashield was available) and with adj ustment for secular trends during 1993-98 by Poisson regression. Findings Hospital admission for intussusception among infants younger than 365 days of age during the Rotashield period compared with previously was 4 % lower (10 cases) by direct comparison and 10% lower (27 cases) by trend c omparison, corresponding to a negative population attributable risk. Among infants aged 45-210 days (target age range for a first Rotashield dose), we estimated an increase in intussusception admissions of 1% (one excess admi ssion) by direct comparison and 4% (4.6 excess admissions) by trend compari son, corresponding to a population attributable risk range of one excess ad mission in 66 000-302 000. Interpretation We found no evidence of increased infant intussusception adm issions during the period of Rotashield availability. The total intussuscep tion admission risk attributable to Rotashield was substantially lower than previous estimates based on studies focusing on the immediate postvaccinat ion weeks.