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]
For people 65 and older, the mRNA flu shot is an accelerated approval
MFLUSIVA is widely described as approved for adults 50 and older, and the FDA product page says exactly that — "approved for use in persons 50 years of age and older," with no further breakdown. The approval letter draws a line the product page does not.[7]
The letter states the vaccine is indicated "in persons 50 years of age and older," then adds: "The indication for persons 65 years of age and older is approved under accelerated approval pursuant to section 506(c) of the Federal Food, Drug, and Cosmetic Act (FDCA) and the regulations for accelerated approval, 21 CFR 601.41."[7]
The practical meaning is a difference in what has been demonstrated. For the 65-and-older group the letter says clinical benefit still has to be verified — "Clinical benefit is evidenced by effects such as demonstration of effectiveness against influenza disease in adults 65 years of age and older" — which is what the required study is for.[7]
The approval can be withdrawn if the confirmatory study does not verify benefit
The letter attaches a condition that summaries rarely mention. It states: "If this required postmarketing study fails to verify that clinical benefit is conferred by Influenza Vaccine, mRNA, or is not conducted with due diligence… we may withdraw this approval."[7]
The study is named and scheduled, not left open-ended: a "Pragmatic, Randomized Study to Evaluate Relative Vaccine Effectiveness of mRNA-1010 Versus High-Dose Influenza Vaccine in U.S. Adults ≥65 Years of Age" (Study mRNA-1010-P910), with study initiation August 31, 2026 and an interim study report due December 31, 2027.[7]
Note the comparator: the required study measures mRNA-1010 against a high-dose influenza vaccine, not against placebo or a standard-dose shot. That is the benchmark the 65-and-older indication has to clear.[7]
Verified facts
Each fact is labelled with its evidence typeEach fact in this section carries its evidence type — either cross-checked against independent sources, or confirmed from a single authoritative record.
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 · independent
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 · independent
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 · independent
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 · independent
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 · independent
Statements and readings
Not counted as facts — each item shows what kind of statement it isFrom here on: statements not counted as facts — single-source reports, the issuing body’s own statements, and this page’s own readings, each labeled.
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] Stated by the issuing body itself (primary source) · not independently verified · 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] Stated by the issuing body itself (primary source) · not independently verified · CDC
The FDA approval letter states that the indication for persons 65 years of age and older is approved under accelerated approval pursuant to section 506(c) of the FDCA and 21 CFR 601.41, while the vaccine is indicated in persons 50 years of age and older.[7] Stated by the issuing body itself (primary source) · not independently verified · FDA approval letter for MFLUSIVA, STN BL 125869/0, August 5, 2026
The letter states that if the required postmarketing study fails to verify clinical benefit, or is not conducted with due diligence, FDA may withdraw the approval.[7] Stated by the issuing body itself (primary source) · not independently verified · FDA approval letter, "ACCELERATED APPROVAL REQUIREMENTS" section
The required postmarketing study is Study mRNA-1010-P910, a pragmatic randomized study of mRNA-1010 versus high-dose influenza vaccine in U.S. adults 65 and older, with study initiation August 31, 2026 and an interim study report due December 31, 2027.[7] Stated by the issuing body itself (primary source) · not independently verified · FDA approval letter, "Accelerated Approval Required Study" section
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
- Body characters
- 3,231
- Sources
- 7 sources adopted
- Model
- claude-fable-5 (review pass)
- Time
- 08/29/2026, 10:00
- Verdict
- Passed
Show revision history (2)
| 08/29/2026, 10:00 | First authored (claude-fable-5) | Created |
| 10/07/2026 | Added source footnotes to four FAQ answers and corrected three against CDC. | Updated |
Corrections
| 10/07/2026 | FAQ corrections against CDC's 'Who Needs a Flu Vaccine' page: the timing answer now gives CDC's September-October window and end-of-October target and drops an unsourced line; the 65+ answer now says any other age-appropriate vaccine rather than a standard-dose one; the higher-risk groups now follow CDC's list (children 6 months through 4 years rather than under 2). | Applied |
Frequently asked
When should I get my flu shot for the 2026-27 season?
CDC says September and October are generally good times for most people who need one dose, and ideally everyone should be vaccinated by the end of October. Most adults, especially those 65 and older, should generally not get vaccinated early (in July or August) because protection may decrease over time.[5]
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.[2]
Which flu vaccine should people 65 and older get?
CDC preferentially recommends three vaccines for adults 65 and older: Fluzone High-Dose, Flublok (recombinant) and Fluad (adjuvanted). If none of the three is available at the time of vaccination, people in this age group can get any other age-appropriate flu vaccine instead.[5]
Who should get a flu vaccine?
Everyone 6 months and older should get a flu vaccine every season, with rare exceptions, per CDC. Vaccination is particularly important for people at higher risk of serious complications. CDC's priority list for shortages includes children aged 6 months through 4 years, pregnant people, adults 50 and older, and people with chronic conditions such as asthma or heart disease or with extreme obesity.[5]
Is the mRNA flu vaccine fully approved for people 65 and older?
The FDA approval letter says the indication for persons 65 and older is approved under accelerated approval pursuant to section 506(c) of the FDCA, while the vaccine is indicated in persons 50 and older. The FDA product page lists only "50 years of age and older" without this breakdown.[7]
What happens if the confirmatory study does not show a benefit?
The approval letter states that if the required postmarketing study fails to verify that clinical benefit is conferred, or is not conducted with due diligence, FDA may withdraw the approval. The required study is mRNA-1010-P910, comparing mRNA-1010 with a high-dose influenza vaccine in adults 65 and older, initiated August 31, 2026 with an interim report due December 31, 2027.[7]
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
- [7] August 5, 2026 Approval Letter — MFLUSIVA (STN BL 125869/0) primary