Flu Shot Effectiveness Dips for 2025-26 Season, But Still Offers Protection
Interim data from the Centers for Disease Control and Prevention (CDC) suggests the 2025-2026 influenza vaccine may be less effective than in recent years. However, experts emphasize that vaccination still provides valuable protection against severe illness, particularly for children and adults.
Vaccine Effectiveness Rates: A Closer Look
Researchers analyzed data from three U.S. Respiratory virus vaccine effectiveness (VE) networks to determine how well the current flu vaccine is performing. The findings, published in the Morbidity and Mortality Weekly Report, reveal varying levels of protection depending on age group and influenza strain.
For children and adolescents under 18, the vaccine demonstrated 38% to 41% effectiveness against outpatient visits due to the flu and 41% effectiveness against influenza-related hospitalizations. Adults aged 18 and older experienced a VE of 22% to 34% against outpatient visits and 30% against hospitalization.
Strain-Specific Protection
The data similarly breaks down effectiveness by influenza type. Against influenza A, VE ranged from 37% (outpatient visits, children/adolescents) to 42% (hospitalization, children/adolescents) and from 30% (hospitalization, adults) to 34% (outpatient visits, adults). Specifically, the vaccine showed 35% and 38% effectiveness against influenza A(H3N2)-associated outpatient visits and hospitalizations, respectively, in younger individuals.
Notably, the vaccine appears more effective against influenza B, with VE ranging from 45% to 71% among children and adolescents and 63% among adults.
Why the Dip in Effectiveness? Antigenic Drift
The reduced effectiveness is likely due to “antigenic drift,” a common phenomenon where influenza viruses constantly mutate. These mutations can produce it harder for the vaccine, designed to target specific strains, to provide optimal protection. The current season is experiencing widespread circulation of an antigenically drifted influenza A(H3N2) strain.
The Importance of Vaccination Despite Lower VE
Despite the lower VE estimates, the CDC emphasizes that influenza vaccination still prevents thousands of hospitalizations and deaths each year. Vaccination doesn’t always prevent infection, but it significantly reduces the risk of severe illness and complications.
Future Trends in Flu Vaccine Development
Researchers are continually working to improve flu vaccine effectiveness. Several promising avenues are being explored:
- Universal Flu Vaccines: These vaccines aim to provide broad protection against all influenza strains, rather than just those predicted to circulate in a given season.
- mRNA Technology: The success of mRNA vaccines for COVID-19 has spurred research into using the same technology for influenza vaccines, potentially allowing for faster development and production.
- Improved Strain Prediction: Efforts to better predict which influenza strains will dominate each season are ongoing, which will support ensure vaccines are a better match.
Frequently Asked Questions
- Is the flu shot still worth getting if it’s less effective? Yes. Even with reduced effectiveness, the flu shot still offers protection against severe illness and complications.
- Who is most vulnerable to the flu? Young children, older adults, pregnant women, and people with certain chronic health conditions are at higher risk of serious flu complications.
- When should I get the flu shot? The CDC recommends getting vaccinated before flu season begins, ideally by the end of October.
Stay informed about influenza and vaccination recommendations by visiting the CDC’s influenza website.
Do you have questions about the flu vaccine? Share your thoughts in the comments below!
