Adjusted relative effectiveness of LAIV4 versus IIV by influenza type, subtype, and age group. aOR, adjusted odds ratio. a Relative effectiveness estimates are expressed as the odds of influenza among LAIV4 recipients compared with IIV recipients and 95% CIs. An OR of <1 suggests lower odds of influenza in LAIV4 recipients compared with IIV recipients. Models are adjusted for age (group or years for age-stratified models), season, calendar time, and site (as a random effect). b Includes the 2013–2014 influenza season through the 2015–2016 season. c Restricted to the 2013–2014 and 2015–2016 influenza seasons. d Restricted to the 2014–2015 influenza season.