Expected Efficacy of the Influenza Vaccine for 2025
Based on the most recent evidence, the 2024-2025 influenza vaccine is expected to have an efficacy of 32-60% in children and adolescents and 36-55% in adults, with higher effectiveness against hospitalization than outpatient visits. 1
Vaccine Composition and Formulation
The 2024-2025 influenza vaccines in the United States are trivalent (containing three virus strains) rather than quadrivalent as in previous years 2:
- A/Victoria/4897/2022 (H1N1)pdm09-like virus
- A/Thailand/8/2022 (H3N2)-like virus
- B/Austria/1359417/2021 (Victoria lineage)-like virus
The influenza B Yamagata lineage has been removed from seasonal vaccines as it has not been detected globally since 2020 3.
Vaccine Effectiveness by Age Group and Setting
Children and Adolescents (<18 years)
Adults (≥18 years)
Older Adults (≥65 years)
- Enhanced vaccines (adjuvanted and high-dose) show significantly better protection:
- Adjuvanted vaccine: 48% effective (95% CI: 42-52)
- Standard-dose vaccine: 33% effective (95% CI: 24-41) 4
Factors Affecting Vaccine Efficacy
Vaccine effectiveness varies based on multiple factors 3:
- Age and health status of the recipient
- Type of vaccine administered
- Types and subtypes of influenza viruses circulating
- Degree of similarity between circulating viruses and those in the vaccine
Historical Context and Expected Benefits
Historically, influenza vaccination has prevented:
- 1.6-7.1 million illnesses
- 790,000-3.7 million outpatient visits
- 39,000-109,000 hospitalizations
- 3,000-10,000 deaths per season 3
Even during seasons with moderate vaccine effectiveness (around 38%), substantial public health benefits have been observed 3.
Special Considerations
- Timing: The CDC and AAP recommend administering influenza vaccines as soon as they become available, ideally by the end of October 2
- Two-dose schedule: Children 6 months through 8 years receiving influenza vaccine for the first time or who received only one dose before July 1,2024, should receive two doses at least 4 weeks apart 2
- Egg allergy: No special precautions are needed for individuals with egg allergy 2
Common Pitfalls to Avoid
- Delaying vaccination to obtain a specific product when an appropriate one is available 2
- Assuming vaccine strains remain constant between seasons 2
- Overlooking the change from quadrivalent to trivalent vaccines in the U.S. for the 2024-2025 season 2
- Waiting too long to vaccinate, as the timing of influenza season onset is unpredictable 3
Conclusion
While the 2024-2025 influenza vaccine shows moderate effectiveness overall, it provides substantial protection against severe outcomes requiring hospitalization. The vaccine remains the most effective method for preventing influenza infection and its complications, particularly for reducing severe disease, hospitalizations, and deaths.