Use of the state immunization information system to assess rotavirus vaccine effectiveness in Connecticut, 2006-2008

Immunization information systems (IIS) contain individual vaccination records and have potential use for evaluating post-licensure vaccine effectiveness (VE). A matched case-control study was performed by using the Connecticut state IIS to calculate rotavirus VE against hospitalization; results were compared with pre-licensure efficacy and with estimates previously obtained by traditional case-control methods using matched controls from medical sources and medical chart abstracted data. Case-patients (n = 54) were vaccine-eligible children with IIS entry and hospitalized for rotavirus gastroenteritis during July 2006-December 2008; each was matched to five control subjects (n = 270) who were randomly selected from IIS based on case-patient's birth date and town of residence. VE of at least one dose was 90.6%, comparable to the pre-licensure efficacy of 96% and to the unadjusted 83.5-90.7% estimates by using traditional case-control methods. IIS can be a convenient and potentially accurate tool for calculating VE.