It's officially fall, which means respiratory virus season is right around the corner, and it's now the best time to get your flu shot, the most effective way to protect yourself against influenza this winter.
The flu is a common and highly contagious respiratory illness that spikes every year in the colder months, sickening millions and killing thousands. Anyone can get sick with influenza, but some people are at higher risk for severe disease and complications.
The seasonal flu vaccine is safe and effective. In addition to preventing illness, it prevents hospitalizations and deaths. Getting vaccinated is easy — in case you missed it, TODAY co-hosts rolled up their sleeves and got their shots live on the show to prove it.
The U.S. Centers for Disease Control and Prevention has approved multiple flu shots for the 2025-2026 season, including standard-dose shots, high-dose shots and nasal mists.
Despite shifting COVID vaccine recommendations, the guidance around influenza vaccines is the same: The CDC recommends flu shots for everyone 6 months and older (with rare exceptions).
When is the best time to get a flu shot this year, and what can we expect for the 2025-2026 flu season? Here's what to know.
What Is the Best Time to Get a Flu Shot?
"The advice has been similar for many years, and really the best time to get the flu shot is before the end of October," Dr. Megan Berman, professor of medicine at the University of Texas Medical Branch, tells TODAY.com.
Another easy way to remember? Get vaccinated by Halloween. "It's corny, but I tell my patients, 'flu before boo,'" says Berman.
The flu shot does not work right away. It takes about two weeks after getting vaccinated for the body to develop enough antibodies to protect against influenza, per the CDC.
Getting the flu shot at this time allows immune protection to build up before flu activity ramps up and peaks, usually between December and February.
What to Expect for the 2025-2026 Flu Season
According to the CDC’s “FluView” surveillance report for the week ending Sept. 20, flu activity is low nationally, but cases are expected to increase in the coming weeks and months.
It’s too soon to tell how the 2025-2026 flu season will unfold. "Flu is predictably unpredictable," says Berman.
The timing, duration and severity of flu season varies from year to year. In the U.S., flu season can begin as early as October and last until as late as May, per the CDC.
Scientists often look to the Southern hemisphere for clues, where flu activity peaks between April and September.
Australia, often a harbinger for flu trends in the U.S.,had a moderately severe 2025 flu season that got off to a late start, per CDC data.
Last year's flu season in the U.S. peaked in early February, Dr. Syra Madad, an infectious disease epidemiologist at Harvard University’s Belfer Center, tells TODAY.com.
The 2024-2025 flu season in the U.S. was "a high severity" season, with 43 million illnesses, 560,000 hospitalizations and 38,000 deaths, the CDC said in a report published last week.
These include 280 pediatric flu deaths, the highest number recorded since the 2009 swine flu pandemic, says Berman.
Who Should Get the Flu Shot?
“Everyone 6 months and older, with rare exceptions, should get a flu vaccine every season,” the CDC says.
Vaccination is one of the best ways to prevent yourself from getting sick or hospitalized and dying from seasonal flu, says Madad.
The flu shot is especially important for individuals at higher risk of severe influenza or complications — such as adults over 65, children under 2, pregnant women and people with chronic conditions, per the CDC.
It’s safe for pregnant people to get the inactivated flu shot, which also provides protection to the baby, per the CDC.
“Influenza is a nasty virus. ... The more we all get vaccinated, the better we protect ourselves and others,” Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, previously told TODAY.com.
Unfortunately, flu vaccine rates are declining, especially among children, says Madad. Last season, nearly 90% of the children who died from flu were unvaccinated, per the CDC.
How Long Does the Flu Shot Last?
The duration of protection from the flu shot varies depending on the person and their immune system, but it generally lasts about six months, the experts say. If you get the vaccine in October, you should be protected through the winter into March.
The new flu shots for the 2025-2026 season are trivalent, meaning they protect against three different flu strains: two influenza A viruses (H1N1 and H3N2) and one influenza B virus.
In the U.S., flu season often starts with A strains being more active and ends with B strains as more active, Schaffner adds, which is why the shot can offer continued protection for months.
Is It Better to Get the Flu Shot Earlier or Later in the Season?
“The biggest benefit is when you get vaccinated before the season starts,” Dr. Albert Ko, infectious disease physician and professor at Yale School of Public Health, previously told TODAY.com.
It is possible to get vaccinated too early, which can cause immunity to wane before the season ends, Berman says.
For most people, as long as you’re getting the flu shot within the recommended timeframe — September to October — it doesn’t matter if you get it earlier or later, experts note.
People who are older or have underlying illnesses should always talk to their doctor about the best time to get a flu shot.
Some children may need two doses of the flu vaccine, which are given at least four weeks apart, per the CDC. These children should get their first flu shot as soon as possible.
“The bottom line is that you don’t want to wait until you’re already going to be at risk of getting influenza to get vaccinated,” Ko said.
When Is It Too Late to Get a Flu Shot?
Although you’ll get the most protection by getting vaccinated by the end of October, it's never “too late” to get the flu shot, the experts emphasize.
“If you’ve never had the flu shot, no matter where you are during the season, you should get it,” said Ko. The flu shot can still provide protection if you get it later in the season.
Which Flu Vaccines Are Available?
There are several different types of flu shots available — the one that is right for you depends on your age, health and other factors. Always talk to your doctor if you have questions.
For the 2025-2026 flu season, the CDC recommends single-dose flu shots formulations "that are free of thimerosal." Thimerosal is a widely-used preservative, which the Department of Health and Human Services voted to remove from all flu vaccines this year.
(Research has repeatedly show that thimerosal is safe, and 96% of vaccines in the U.S. were already made without thimerosal prior to the vote, says Madad.)
According to the CDC, available vaccines for 2025-2026 include:
Standard-dose, egg-based flu shot: These contain inactivated (killed) flu virus grown in eggs and are recommended for everyone ages 6 months to 64 years.
High-dose egg-based flu shot: This produces a stronger immune response and is approved for individuals aged 65 and older.
Standard-dose cell-based flu shot: This egg-free flu shot contains virus grown in cell cultures and is approved for people 6 months and older.
Adjuvanted egg-based flu shot: This shot approved for people 65 and older contains an adjuvant, which creates a stronger immune response.
Recombinant flu shot: This egg-free flu shot is made using recombinant technology and is approved for individuals 9 and older.
Nasal spray vaccine: This nasal mist uses live, attenuated (weakened) virus, and it’s approved for people 2-49 years old — but not pregnant or immunocompromised individuals.
Ahead of this season, the Food and Drug Administration approved a nasal mist that can be self-administered or given by a caretaker at home.
Flu Shot Side Effects
Side effects from the flu vaccine are generally mild, according to the CDC, and may include:
- Redness or soreness at the injection site
- Mild headache
- Fever
- Fatigue
- Muscle aches
You can’t get the flu from the flu shot, the experts stress.
How Effective Is the Flu Shot?
The efficacy of seasonal flu vaccines varies from year to year, but studies show it can reduce the risk of illness by 40-60% when most of the virus strains in the vaccine match the strains circulating that season.
During the Southern Hemisphere's 2025 flu season, influenza vaccines reduced flu-related outpatient visits by about 50% and hospitalizations by 49%, per a new CDC report.
The effectiveness of the flu vaccine is usually determined after the season ends, when there’s more data available.
"Even if the seasonal flu vaccine is not a great match to the circulating strains, it still protects you against severe illness, hospitalization and death," says Madad.
Can You Still Get the Flu After Getting the Flu Shot?
Some vaccinated people may still get sick with the flu. However, the flu shot reduces the severity of illness in people who get infected after vaccination, per the CDC.
“By getting flu vaccine, you take a more serious infection and you turn it into a milder one,” said Schaffner. So just because the flu shot doesn’t always prevent infection does not mean it’s not working, the experts emphasize.
The most common flu symptoms include a fever, chills, body aches, headache, fatigue, a cough, sore throat and stuffy nose.
If you get the flu, the CDC recommends staying home for at least 24 hours after your fever is gone (except to seek medical care). Always contact your doctor if you are in a high-risk group, feeling very sick or have concerns.
There are flu antivirals available, such as Tamiflu, which require a prescription and can reduce disease severity. Most people will recover from flu without needing medical care, the experts note.
Can I Get a Flu Shot and COVID-19 Vaccine at the Same Time?
Yes, you can and should get your flu shot and COVID-19 vaccine at the same time, Schaffner said. However, you may want to get them in different arms if you're prone to soreness.
“It’s safe and it’s very effective,” Berman adds.
The updated COVID-19 vaccines for 2025-2026 are available to everyone ages 6 months and older who wants one, but new restrictions may make it harder for certain groups to get the shots, TODAY.com reported previously.
The RSV vaccine is also available for pregnant people (to prevent RSV in newborns), adults ages 75 and older, and adults ages 60 to 74 at higher risk of severe RSV.
How to Prevent the Spread of Flu
In addition to getting vaccinated, you can take everyday actions to prevent the spread of flu and other respiratory viruses:
- Stay home when sick.
- Avoid sick people.
- Cover coughs and sneezes.
- Wash your hands often.
- Disinfect shared surfaces.
