Objectives: To examine pharmacy-based influenza vaccination using diffusion of innovation theory.
Methods: We used 1993 to 2013 Behavioral Risk Factor Surveillance System data to generate weighted prevalence rates of influenza vaccination, stratified by age (18-64 years vs ≥ 65 years) and state of residence. The diffusion of innovation theory adopter categories were residents of states allowing pharmacist vaccination before 1996 ("innovator/early adopters"), between 1996 and 1998 ("early majority"), between 1999 and 2004 ("late majority"), and in 2007 or later ("laggards").
Results: For adults aged 18 to 64 years, vaccination rates were similar before the innovation (1993), diverged as the innovation reached the majority (2003), and were significantly lower for laggard states by 2013. Younger adults' vaccination rates steadily increased from 12% to 16% in 1993 to 29% to 36% in 2013. For older adults, there was no significant difference in vaccination rates between adopter categories in any year and no advantage associated with adoption category.
Conclusions: Key features of pharmacy-based vaccination, including relative advantage and compatibility, are most relevant to younger adults; different interventions are warranted for older adults.