Leveraging state immunization information systems to measure the effectiveness of rotavirus vaccine.

OBJECTIVE: Electronic immunization information systems (IISs) are now established in almost all US states. We used the IIS in Minnesota, Georgia, and Connecticut for immunization data and as the source of 1 of 2 control groups to measure pentavalent rotavirus vaccine (RV5) effectiveness (VE) using case-control methodology. PATIENTS AND METHODS: Case-subjects were vaccine-eligible children who presented to 1 of 5 hospitals or emergency departments with gastroenteritis and had rotavirus antigen detected in stool during any of 3 rotavirus seasons (2007-2009). Two control groups were used: children with gastroenteritis who tested negative for rotavirus and children from the IIS matched by zip code and birth date. In Minnesota and Georgia, immunization records for rotavirus-positive and -negative children were also obtained from providers.
RESULTS: Overall, 402 (96%) rotavirus case-subjects and 825 (97%) rotavirus-negative controls who met eligibility criteria were found in the IISs. Ten IIS controls were identified for each case. VE estimates for RV5 were similar across control groups, immunization data sources, and states. VE point estimates for 3 vs 0 doses were 89% to 94% among children aged 8 months or older and 86% to 92% among those aged 24 months or older. VE for 2 doses was ≥90% among children aged 8 months or older, and VE for 1 dose was 66% among those aged 6 weeks through 5 months.
CONCLUSIONS: Three RV5 doses confer sustained protection against rotavirus disease during the first 3 years of life in US children. Two RV5 doses also seem to provide good protection. IISs can be valuable tools for assessing the effectiveness of vaccines administered to young children.