How effective are influenza vaccines?

The influenza vaccine is the best way to protect against influenza. How well the vaccine works varies from season to season. It depends on how well-matched the influenza vaccine is with the viruses circulating during the season and on the health status and age of the person being vaccinated. When the influenza vaccine is well-matched with the circulating viruses, it prevents influenza in about 60% to 80% of adults and youth receiving the vaccine. It is less effective in seniors and elders, but studies have shown that the influenza vaccine decreases the incidence of pneumonia, hospital admissions, and death in the elderly population.