How Effective Is The Flu Vaccine? File

38%–41% effective against outpatient visits and 41% against hospitalizations.

22%–34% effective against outpatient visits and 30% against hospitalizations. How Effective is the Flu Vaccine?

30%–42% effective depending on age and setting. Influenza B: 45%–71% effective. Why Effectiveness Varies How Effective is the Flu Vaccine?