Comparison of the Effectiveness of Trivalent Inactivated Influenza Vaccine and Live, Attenuated Influenza Vaccine in Preventing Influenza-Like Illness Among US Military Service Members, 2006–2009

Abstract : Influenza is a significant cause of morbidity, and vaccination is the preferred preventive strategy. Data regarding the preferred influenza vaccine type among adults are limited. The effectiveness of 2 currently available influenza vaccines [live, attenuated influenza vaccine (LAIV) versus trivalent inactivated influenza vaccine (TIV)] in preventing influenza-like illness (ILI) were compared among US military members (aged 18 49 years) during 3 consecutive influenza seasons (2006 2009). ILI, influenza, and pneumonia events post-vaccination were compared between vaccine types using Cox proportional hazard models adjusted for sociodemographic factors, occupation, and geographic area. A total of 41,670 vaccination events were evaluated, including 28,929 during 2 well-matched seasons (2006 2007 and 2008 2009; LAIV n = 22,734, TIV n = 6195) and 12,741 during a poorly matched season (2007 2008; LAIV n = 9447; TIV n = 3294). ILI incidence rates for LAIV and TIV were 139 and 127 cases per 1000 person-seasons for the well-matched seasons, and 150 and 165 respectively, for the poorly matched season. In the multivariable models, there were no differences in ILI events by vaccine type (well-matched seasons: hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.90 1.06; poorly matched: HR, 1.00; 95% CI, 0.90 1.11). There were also no differences in influenza and/or pneumonia events by vaccine group. Between 2006 2009, TIV and LAIV had similar effectiveness in preventing ILI and influenza/pneumonia events among healthy adults