Use Of The State Immunization System To Assess Influenza Vaccine Effectiveness Among Children 6-35 Months Of Age In New Haven County, Ct, 2003-2012

Population-based immunization information systems have been used successfully to assess vaccine effectiveness (VE) in children. The Connecticut Immunization Registry and Tracking system (CIRTS) and the Connecticut Emerging Infections Program (CTEIP) provided the opportunity to evaluate influenza VE among children 6-35 months of age in New Haven County, CT, 2003-2012. A total of 104 case children and 520 date-of-birth- and zipcode-matched controls were studied. The VE in matched analysis of full vaccination compared to no vaccination was 31% (95% CI, \u3c0%-69%; p=0.38). The VE of at least one dose of influenza vaccine compared to no vaccination was 37% (95% CI, \u3c0%-63%; p=0.09). Our study suggests that the overall total VE is unlikely to be greater than 69% among children 6-35 months of age and having had at least one dose of influenza vaccine could be protective from influenza-caused hospitalization compared with never having been vaccinated. This study should be extended for several more influenza seasons to determine a range of effectiveness that does not include zero