Flu shot delivers strong protection: 40% fewer hospitalizations in 2024–2025 season

The flu vaccine proved its worth during a particularly active 2024–2025 influenza season. A CDC-led study analyzing over 6,100 hospitalized adults across 26 US medical centers found that vaccination reduced the risk of flu-related hospitalization by 40% — and the protection held up across all adult age groups and both major influenza A subtypes (H1N1 and H3N2).

Beyond keeping people out of the hospital, the vaccine also shielded those who were admitted from the worst outcomes. Vaccinated patients were 58% less likely to need ICU care or invasive organ support, and 52% less likely to die — meaningful numbers during a season with sustained elevated flu activity. One notable caveat: immunocompromised patients saw little to no benefit (VE of just 7%), highlighting a persistent gap in protection for this vulnerable group.

Key Takeaways:

• Overall VE against hospitalization: 40% (50% for ages 18–49; 41% for 50–64; 39% for 65+)
• VE against ICU admission and invasive organ support: 58%
• VE against death: 52%
• Immunocompromised patients: no significant protection observed (VE: 7%)
• H3N2 protection was lower in adults 65+ (34%) vs. ages 18–64 (58%)

Why it matters: These findings reinforce the value of annual flu vaccination for the general adult population — especially for preventing severe illness. But they also underscore an urgent need for better strategies to protect immunocompromised patients, who remain highly vulnerable despite vaccination.