Influenza Vaccine Effectiveness and Recommendations

Age-Specific Effectiveness Patterns

The Centers for Disease Control and Prevention recommends that healthy adults under 65 years achieve 70-90% protection against influenza when strains are well-matched, while elderly persons show lower antibody responses but still gain critical protection against severe outcomes 1, 2
Among elderly persons living outside nursing homes, the vaccine is 30-70% effective in preventing hospitalization for pneumonia and influenza 1, 2
Among nursing home residents, the vaccine is 30-40% effective against influenza illness, but 50-60% effective in preventing hospitalization/pneumonia and 80% effective in preventing death 1, 3
Among healthy adults <65 years, the vaccine is 70-90% effective when vaccine and circulating viruses are well-matched 2, 4

Influenza activity can persist through February, March, or later, highlighting the importance of continued vaccination throughout the influenza season 5
The vaccine's effectiveness wanes over time, approximately 7-11% per month, emphasizing the need for timely vaccination 5
Delaying vaccination in patients with minor illnesses without fever can lead to missed opportunities for protection 5