Influenza — The Goal of Control

Annual administration of inactivated influenza vaccine to older adults has long been recommended by public health authorities.¹ The risks of influenza-related complications, hospitalizations, and deaths increase with age, as does the prevalence of underlying medical conditions. Prospective, randomized, controlled studies have demonstrated that inactivated vaccine is protective against laboratory-confirmed influenza in young adults and, according to much more limited data, in older adults as well.²

Given the demonstrated effectiveness of the vaccine, one might have expected that as the rates of vaccination increased, there would be a corresponding decrease in flu-related hospitalizations and deaths. Instead, the opposite has occurred, with winter hospitalizations and deaths increasing during this period.⁶ There are many possible explanations for this phenomenon, but this observation has called into question previous studies showing large effects on the rates of death from any cause. Many of the previous cohort studies have been limited in that they analyzed only one or two seasons or were conducted at a single site, since reported morbidity due to influenza may vary significantly by season and region.⁷ The study reported by Nichol et al. in this issue of the Journal⁸ addresses many of these concerns and increases our confidence in the benefits of influenza vaccination for older adults.

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