US Flu Season 2026-27 Vaccine Guide — All 3 Strains Updated, Best Timing Sept-Oct
For 2026-27, all three US flu vaccine strains were updated, including new H3N2 subclade K coverage. CDC advises everyone 6 months and older get a flu shot, ideally in September or October.
What's in the 2026-27 flu shot
The 2026-27 U.S. flu vaccines carry an unusually large update: all three virus components changed from the previous season's formula. FDA made the composition recommendation on March 13, 2026, a day after its Vaccines and Related Biological Products Advisory Committee voted unanimously (7-0) for the new strains. The headline change is the A(H3N2) component, retargeted at the subclade K virus that drove much of the 2025-26 season's illness.[1][3][4]
Egg-based vaccines for 2026-27 contain an A/Missouri/11/2025 (H1N1)pdm09-like virus, an A/Darwin/1454/2025 (H3N2)-like virus, and a B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like virus. Cell-based and recombinant vaccines use the same H1N1 strain but substitute A/Darwin/1415/2025 for H3N2 and B/Pennsylvania/14/2025 for the B component.[1][3]
Who should get vaccinated, and when
CDC's baseline recommendation is unchanged: everyone 6 months and older should get a flu vaccine every year. September and October are the best months for most people because protection can decrease over time; vaccinating too early (July-August) is generally discouraged for older adults for the same reason, while vaccination continues to be offered throughout the season as long as flu viruses circulate. Adults 65 and older should ask for one of three preferentially recommended products — Fluzone High-Dose, Flublok, or Fluad — which are designed to produce a stronger immune response in older adults. New this season, the mRNA-based mFLUSIVA (approved for adults 50+) is expected to reach pharmacies alongside the traditional shots.[2][5][6]
Verified facts
Cross-checked against 2+ independent sourcesThis section contains facts cross-checked against multiple sources.
On March 13, 2026, the FDA recommended updating all three virus components of 2026-27 U.S. seasonal flu vaccines compared with 2025-26, including a change to protect against the influenza A(H3N2) subclade K virus that spread widely during the 2025-26 season.[1][2][4] 3 sources
FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) met March 12, 2026 and voted unanimously 7-0 to recommend the updated strain selections.[3][4] 2 sources
Egg-based 2026-27 vaccines contain A/Missouri/11/2025 (H1N1)pdm09-like, A/Darwin/1454/2025 (H3N2)-like, and B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like viruses; cell- and recombinant-based vaccines use A/Darwin/1415/2025 for H3N2 and B/Pennsylvania/14/2025 for B/Victoria.[1][3] 2 sources
CDC recommends that everyone 6 months and older get a flu vaccine every year, and September and October are generally the best months to be vaccinated for most people.[5][6] 2 sources
For adults 65 and older, CDC preferentially recommends three vaccines: high-dose inactivated (Fluzone High-Dose), recombinant (Flublok), or adjuvanted inactivated (Fluad).[5][6] 2 sources
Reported, not confirmed
Not cross-checked — do not read as factFrom here on: claims and speculation that are not cross-checked.
mFLUSIVA, an mRNA influenza vaccine approved for adults 50 and older, is expected to be available for the first time during the 2026-27 season.[2] single-source ×1 · CDC 2026-2027 flu season page
Vaccination remains worthwhile after October: CDC says getting vaccinated any time during the season is fine as long as flu viruses are circulating and vaccine is available.[5] single-source ×1 · CDC
Timeline
- 2026-03-12
FDA advisory committee (VRBPAC) meets and votes 7-0 to recommend updated 2026-27 flu vaccine strains.[3][4]
- 2026-03-13
FDA issues its official 2026-27 U.S. influenza vaccine composition recommendation — all three components updated.[1]
- 2026-09-01
CDC-recommended vaccination window: September and October are the ideal months for most people to get the 2026-27 flu shot.[5][6]
- Model
- claude-fable-5
- Time
- 08/29/2026, 10:00
- Tokens
- 8,000
- Sources
- 6 sources adopted
- Model
- claude-fable-5 (review pass)
- Time
- 08/29/2026, 10:00
- Tokens
- 3,000
- Verdict
- Passed
| 08/29/2026, 10:00 | First authored (claude-fable-5) | Created |
Frequently asked
When should I get my flu shot for the 2026-27 season?
CDC recommends September or October for most people, since protection can wane over time. If you miss that window, vaccination is still recommended any time flu viruses are circulating.
What's different about this year's flu shot?
All three strains were updated from the 2025-26 formula. The biggest change targets the influenza A(H3N2) subclade K virus, which spread widely during the 2025-26 season.
Which flu vaccine should people 65 and older get?
CDC preferentially recommends three options for adults 65+: Fluzone High-Dose, Flublok (recombinant), or Fluad (adjuvanted). If none is available, a standard-dose flu vaccine is recommended instead of skipping vaccination.
Who should get a flu vaccine?
Everyone 6 months and older, per CDC. Vaccination is especially important for adults 65+, children under 2, pregnant people, and those with conditions such as asthma, heart disease, or obesity.
Official links
Sources
- [1] Influenza Vaccine Composition for the 2026-2027 U.S. Influenza Season primary
- [2] 2026-2027 Flu Season primary
- [3] FDA VRBPAC Votes to Recommend Influenza Vaccines for 2026-2027 Season
- [4] FDA Panel 2026-2027 Flu Vaccine Recommendation Takes Aim at Subclade K
- [5] Who Needs a Flu Vaccine primary
- [6] What to Know About the 2026-2027 U.S. Flu Season