Flu season is approaching in the Northern Hemisphere, and the Centers for Disease Control and Prevention (CDC) has restated its core advice for 2026-27: nearly everyone aged 6 months and older should get a flu vaccine, ideally by the end of October. This guide covers who that includes, how the timing works and what the most recent full season showed.
What does CDC recommend for the 2026-27 season?
According to CDC guidance updated September 1, 2026, “Everyone 6 months and older in the United States, with rare exception, should get a flu vaccine every season.” The agency’s interim guidance for 2026-27 adds that the seasonal influenza recommendations from the July 2025 immunization schedule remain in effect.
All flu vaccines in the United States this season are trivalent, meaning they protect against three influenza viruses. The vaccine is reformulated regularly because influenza viruses change constantly and because immunity from vaccination declines over time. That is why a shot from last year does not cover this one.
The recommendation is broad on purpose. Flu is not only a risk for the elderly or the chronically ill. CDC describes people 65 and older and people with chronic conditions as being at higher risk of serious complications, including pneumonia and worsening of heart failure, asthma or diabetes. But healthy people can also become seriously ill, and vaccinating widely reduces spread to those who are most vulnerable.
When is the best time to get vaccinated?
CDC says that for most people who need one dose, September and October are generally good times, and that everyone should ideally be vaccinated by the end of October. Two practical facts sit behind that timing:
- Antibodies take about two weeks to develop after vaccination, so the shot works best when it is in place before flu viruses begin spreading in your community.
- Protection can decline over the course of a season, so going too early has a cost.
For that second reason, CDC advises against vaccination in July and August for most groups. There are exceptions. Early vaccination can be considered for people who may not be able to return later, and for pregnant people in the third trimester, because vaccination during pregnancy helps protect infants.
Missing October is not a reason to skip the shot. CDC says vaccination should continue after October and throughout the season for as long as flu viruses are circulating and unexpired vaccine is available.
Which vaccine is the right one for each group?
Most people under 65 can receive any age-appropriate vaccine. CDC does not express a preference among inactivated, recombinant or live attenuated nasal spray options for this group. Adults 65 and older are treated differently.
| Group | CDC guidance for 2026-27 |
|---|---|
| Ages 6 months to 8 years | Some children need two doses, at least four weeks apart |
| Adults 18 to 64 | Any age-appropriate vaccine; no preferred product |
| Adults 65 and older | Preferred: high-dose, recombinant or adjuvanted vaccine; any other age-appropriate vaccine if those are unavailable |
| Pregnant people | Inactivated or recombinant vaccine; nasal spray not used in pregnancy but can be used after delivery |
The nasal spray is licensed for ages 2 to 49 and is not recommended for pregnant or immunocompromised people. People with an egg allergy may receive any age-appropriate flu vaccine, egg-based or not.
Flu vaccines can usually be given at the same visit as other vaccines, with injections placed at separate sites. Anyone with questions about a specific product, a past allergic reaction or an underlying condition should ask a clinician or pharmacist.
How bad was the last full flu season?
The 2024-25 season is the most recent one for which CDC has published end-of-season burden estimates, and it was a harsh one. CDC classified it as high severity across all ages and within each age group, the first high-severity season since 2017-18.
CDC’s estimates, as of its March 2026 update and still described as preliminary until finalization expected in 2027, were:
| Measure | Estimated burden, 2024-25 |
|---|---|
| Flu illnesses | 51 million |
| Outpatient medical visits | 23 million |
| Hospitalizations | 710,000 |
| Deaths | 45,000 |
CDC also notes that flu deaths in children are under-reported. It estimated 790 pediatric deaths for the season and had received 290 laboratory-confirmed pediatric death reports as of February 14, 2026. These are modeled figures: CDC combines illness, hospitalization and death data with statistical models, because many people with flu are never tested.
What did vaccination prevent?
The same CDC analysis estimates how much worse the season would have been without vaccination. It credits vaccination with preventing about 10 million illnesses, 5 million medical visits, 180,000 hospitalizations and 12,000 deaths.
A simple worked example shows what that means in proportion. Add the prevented hospitalizations to the estimated actual ones and you get roughly 890,000 hospitalizations in a world without vaccination (710,000 plus 180,000). The 180,000 prevented is about 20% of that total. Deaths follow a similar pattern: 45,000 plus 12,000 is 57,000, of which 12,000 is about 21%. For illnesses, 10 million of an implied 61 million is about 16%.
These are illustrative calculations from modeled estimates, not precise counts. They do show why public health agencies emphasize vaccination even in seasons when the vaccine is an imperfect match. A shot that prevents roughly one in five hospitalizations, across a population this large, spares a great many families.
How well does the flu shot work?
Effectiveness varies by season, depending on a person’s age and health and how closely the vaccine viruses match those circulating. CDC says that in seasons when the match is good, vaccination reduces the risk of needing a doctor visit for flu by 40% to 60%.
That means the shot is not a guarantee against infection, and it is reasonable to say so plainly. What it does more reliably is reduce severity. CDC cites a 2021 study in which vaccinated adults who were hospitalized with flu had a 26% lower risk of ICU admission and a 31% lower risk of flu death than unvaccinated adults.
The vaccine tends to work best in healthy younger adults and older children. Some older people and people with certain chronic illnesses may develop less immunity, which is one reason the preferred vaccines for those 65 and older are stronger formulations.
What side effects should people expect?
For the injected vaccine, CDC lists soreness, redness or swelling where the shot was given, plus headache, fever, muscle aches, nausea and fatigue. The NHS in the United Kingdom, which runs its own autumn program, describes the common effects as mild and usually gone within one to two days. Injected flu vaccines do not contain live virus, so they cannot cause flu.
Serious effects are uncommon. CDC notes a small increased risk of Guillain-Barré syndrome and a very remote chance of a severe allergic reaction. People who have had a severe allergic reaction to a previous dose or to a vaccine ingredient should speak to a clinician before vaccination, and the NHS advises waiting until recovery if you have a high temperature.
How does flu vaccination connect to other health priorities?
Flu is a useful reminder that infections are a system-level problem. Severe flu raises the risk of bacterial pneumonia, which often means antibiotic treatment, and our coverage of WHO’s findings on antibiotic resistance explains why preventing infections in the first place matters so much. Older adults, who bear a disproportionate share of severe flu, are also a fast-growing group, as the world’s aging population shows.
Practical matters count too. People who feel unwell this winter can often start with telehealth for an initial assessment, though vaccination itself is typically done in person at a clinic or pharmacy. And because fatigue and poor rest make any illness harder to shake, the evidence on better sleep is worth a look as the colder months arrive.
A short autumn checklist
Reading the guidance as a whole, a few plain points emerge:
- Aim for September or October, and by the end of October if you can.
- Do not wait for a perfect moment; later is still better than not at all while flu is circulating.
- Parents of children under 9 should check whether two doses are needed, since the doses must be at least four weeks apart.
- Adults 65 and older should ask for a high-dose, recombinant or adjuvanted vaccine, if available.
- Anyone with an allergy history or a chronic condition should talk to a clinician about which product suits them.
The case for acting before the season peaks
The most recent full flu season was among the most severe in years, and CDC’s own modeling suggests vaccination kept it from being considerably worse. With protection taking about two weeks to build, the weeks before flu activity climbs are the ones that count. For most people, the decision is a small appointment with a well-understood trade-off.
This article is general information and is not medical advice. Speak to a doctor, pharmacist or other qualified clinician about your own vaccination needs.
Sources: Centers for Disease Control and Prevention; National Health Service
