Can You Give the 2025 Flu Vaccine Now and the 2026 Vaccine Once Available?
Yes, you should administer the 2024-2025 influenza vaccine now (if not already given), and then administer the 2025-2026 vaccine once it becomes available next season—annual influenza vaccination is recommended every year for all persons aged ≥6 months, with each season's vaccine formulated to match anticipated circulating strains. 1
Annual Vaccination is Standard Practice
Influenza vaccination is recommended annually because immunity wanes over time and vaccine formulations change each year to match predicted circulating viral strains. 1
The 2024-2025 season vaccine contains different viral components than the 2025-2026 vaccine will contain, as the World Health Organization updates recommendations based on global surveillance data. 1
No recommendation exists for revaccination (booster doses) within the same influenza season for persons who have already been fully vaccinated—you wait until the next season's vaccine becomes available. 1
Timing for Current Season (2024-2025)
If you haven't received the 2024-2025 vaccine yet:
Administer it now, as vaccination should continue throughout the influenza season as long as viruses are circulating and unexpired vaccine is available. 1, 2
Influenza activity can persist through February, March, or even April in some years, and adults develop peak antibody protection approximately 2 weeks after vaccination. 2, 3
Do not delay vaccination due to concerns about "optimal" timing once we're in the season—the primary goal is ensuring vaccination occurs before or during influenza activity. 2
Timing for Next Season (2025-2026)
When the 2025-2026 vaccine becomes available:
Ideally vaccinate during September or October 2025 for most adults and children requiring only one dose. 1, 2
For most adults (particularly those aged ≥65 years) and pregnant persons in the first or second trimester, avoid vaccination during July and August 2025 unless there is concern that later vaccination might not be possible, due to documented waning of vaccine-induced immunity. 1, 2
Children aged 6 months through 8 years who need 2 doses should receive their first dose as soon as vaccine becomes available (including July-August if necessary), with the second dose at least 4 weeks later, ideally by the end of October. 1, 2
Key Evidence on Vaccine Waning
Multiple observational studies demonstrate that vaccine effectiveness decreases over time within a single season, with waning occurring at approximately 7% per month for influenza A(H3N2) and influenza B, and 6-11% per month for influenza A(H1N1)pdm09. 1
Despite waning, vaccine effectiveness remains greater than zero for at least 5-6 months after vaccination. 1, 3
This waning effect is the primary reason why vaccination too early in one season (e.g., July-August for most adults) is discouraged, and why annual revaccination with the updated formulation is necessary. 1
Common Pitfalls to Avoid
Don't assume one flu vaccine provides multi-year protection—each season requires a new vaccine due to both viral evolution and immunity waning. 1
Don't wait for "perfect" timing if it means missing vaccination opportunities—getting vaccinated late in the season is better than not getting vaccinated at all. 2, 3
Don't confuse within-season revaccination (not recommended) with annual vaccination (strongly recommended)—these are distinct concepts. 1