When's the best time to get your flu shot?
As summer comes to an end, pharmacies across the country are rolling out seasonal influenza vaccines for everyone ages 6 months and older. Although flu season has not yet stared in the United States, experts are already spreading the word about the best time to get the flu shot for protection all winter long.
The flu is a common and highly contagious respiratory illness caused by influenza viruses. In the U.S., flu season usually occurs during the fall and winter months. Influenza activity tends to ramp up in October then peaks between December and February.
According to the U.S. Centers for Disease Control and Prevention’s “FluView” weekly surveillance report for the 2024-25 season, flu activity remains low nationally, and less than 200 cases were reported during the week ending Aug. 31.
However, cases are expected to increase in the coming weeks and months. As flu season approaches, experts are urging Americans to be cautious and get their flu shots on time this year.
What do we know about the 2024-2025 flu season so far, when is the best time to get a flu shot this year, and how else can you protect yourself? We spoke to experts to answer all of your questions.
When is the best time to get a flu shot?
“The best time to get the flu shot is the end of September and during October,” Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, tells TODAY.com. The CDC recommends getting the flu vaccine before October ends.
Getting the flu shot at this time allows immune protection to build before the flu activity ramps up, and it makes it more likely that the protection will last through the winter, according to Schaffner.
The flu shot does not work right away because it takes time for the body to develop antibodies, which help fight off the virus. It takes about two weeks after getting vaccinated for the flu shot to provide full protection, per the CDC.
People should aim to get vaccinated before flu activity peaks, experts say. “You don’t want to get vaccinated during the flu season. ... The biggest benefit is when you get vaccinated before the season starts,” Dr. Albert Ko, an infectious disease physician and professor of public health, epidemiology and medicine at Yale School of Public Health, previously told TODAY.com.
Some children may need two doses of the flu vaccine, which are given at least four weeks apart, per the CDC. For those children, the it is recommended to get the first dose as soon as possible.
What can we expect for the 2024-2025 flu season?
It’s difficult to tell how the 2024-2025 flu season will unfold at this point. The timing and duration of flu season varies from year to year. It can start as early as October, and significant activity can continue as late as May, according to the CDC.
Researchers often look to the Southern hemisphere for clues, as flu activity in temperate regions peaks earlier in the year, between April and September, per the CDC.
“It’s not a direct predictor of what happens here in the U.S.,” said Ko. However, it can offer some insight into what kind of flu season the Northern hemisphere may experience.
Australia, which is often viewed as a harbinger for flu trends in the U.S., had a moderately severe 2024 flu season, says Schaffner.
Influenza activity seems to have returned to pre-pandemic levels. “It looks as though flu is back to its conventional seasonal patterns,” Schaffner adds.
However, the severity of flu season in the U.S. has always varied from year to year, even before the pandemic, according to Ko, so it’s important for people to prepare regardless.
How to protect yourself during flu season
Fortunately, there's a safe way to build up immunity and protect yourself ahead of flu season: the seasonal flu vaccine, which the CDC recommends for everyone ages 6 months and older.
In addition to protecting against influenza viruses, the flu shot helps reduces the burden of flu illness, hospitalizations and deaths.
Influenza sickens millions of people and causes 10,000 to 52,000 deaths in the U.S. every year during flu season, Andrew Pekosz, Ph.D., virologist at the Johns Hopkins Bloomberg School of Public Health, previously told TODAY.com. “It’s not something that is insignificant in terms of how much danger it poses to the population,” Pekosz said.
Even if you've never gotten a flu shot before, it's not too late to start. The flu shot is widely available and free under most health insurance plans.
"Influenza is a nasty virus, particularly for older, frail people and people with underlying illnesses. But the more we all get vaccinated, the better we protect ourselves and others," says Schaffner.
How long does the flu shot last?
How long protection from the flu shot lasts varies by person and timing of the flu shot, but generally if you get the vaccine in October, protection should last through the winter into March, according to experts.
"Younger, healthier people who have a more robust immune systems may get protection well beyond the winter," says Schaffner.
All of the flu shots for the 2024-2025 season are trivalent, meaning they protect against three different flu viruses. The new shots will include two influenza A viruses (H1N1 and H3N2) and one influenza B virus, per the CDC. “We include different strains because more than one strain is usually active at any one time,” says Schaffner.
Occasionally the season starts with A strains being more active and ends with B strains being 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?
It's better to get the flu shot early in the season, before influenza activity ramps up. The CDC guideline is to get vaccinated before the end of October. "The greatest protection, of course, (comes from) when you get it before the season starts,” said Ko.
For most people, as long as you’re getting the flu shot within the recommended timeframe — late September through October — it doesn’t matter if you get it earlier or later, experts note.
“(For) people who are older or have underlying chronic illnesses, the timing of the vaccine is more important because their immune systems don’t respond optimally,” says Schaffner. “We ask them to wait until October to get the vaccine because we want the protection to extend through the entire winter season into March.”
Children who need two doses should schedule their first flu shot appointment right away, NBC News previously reported.
In any case, aim to get your flu shot before Halloween. “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. "It's a preventive vaccine."
When is it too late to get a flu shot?
Although you'll get more protection by getting vaccinated by the end of next month, it is 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 when flu activity peaks, according to the CDC.
“The timing of the flu shot is kind of like timing the stock market. You really don’t want to think too much about it — you just sort of have to get it when you can,” said Pekosz.
It’s hard to predict when this flu season will end, but based on pre-pandemic trends, flu activity will likely wind down in April or May.
Which flu vaccines are available?
There are several different types of flu shots available — the one that is appropriate for you will depend on your age, health status, allergies and other factors. “It’s always good to talk to a primary health care provider who knows you well,” said Ko.
According to the CDC, these are the influenza vaccines available for the 2024-2025 season:
Standard dose flu shot: These vaccines are manufactured using inactivated (killed) influenza virus grown in eggs and recommended for everyone aged 6 months to 64 years (including pregnant women), per the CDC.
High-dose flu shot: This egg-based flu shot contains four times the antigen of the standard-dose, inactivated virus vaccines to produce a stronger immune response in the body. It’s approved for individuals 65 and older, per the CDC.
Cell-based flu shot: This flu shot contains virus that was grown in cell culture, so it is completely egg-free, and it’s approved for people 6 months and older, per the CDC.
Adjuvanted flu shot: This is an egg-based flu shot approved for people 65 and older that contains an adjuvant, which makes an individual have a stronger immune response, per the CDC.
Recombinant flu shot: This is an egg-free flu shot made using recombinant technology, which contains three times the antigens of standard-dose flu shots, per the CDC, and it is approved for adults aged 18 and older.
Nasal spray vaccine: This nasal mist uses live, attenuated (weakened) virus, and it’s approved for people from 2 to 49 years of age, Ko said, but it is not recommended for pregnant or immunocompromised individuals.
For people aged 65 and older who are at higher risk, three vaccines are preferentially recommended by the CDC: the high-dose shot, the adjuvanted shot and the recombinant shot, says Schaffner.
It's safe for pregnant people to get the flu shot during any trimester, which also helps protect the baby after birth, per the CDC.
Flu shot side effects
Side effects from the flu vaccine are generally mild and, according to the CDC, 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, Pekosz said. If you have questions, always talk to your doctor.
How effective is the flu shot?
The efficacy of seasonal flu vaccines varies from year to year, but studies show that it can reduce the risk of flu illness by 40% to 60% when most of the virus strains in the vaccine match the strains circulating that season, according to the CDC.
“There’s a very good match between what’s in our vaccine and the circulating strains in Australia, (and) the influenza virus hasn’t mutated in a way that has us especially concerned,” says Schaffner.
However, it's hard to tell how well the flu shots for the 2024-2025 season will work at this point. The effectiveness of the flu vaccine is usually determined towards the end of the season or afterwards, when there's more data available.
Can you still get the flu after getting the flu shot?
Some people who get the influenza vaccine may still get sick with the flu.
However, there is evidence that the flu shot reduces the severity of illness in people who get infected after vaccination, per the CDC. The flu shot can also help prevent flu-related complications in individuals with chronic health conditions.
So just because the flu shot doesn’t always prevent infection does not mean it’s not working, the experts emphasize.
“By getting flu vaccine, you take a more serious infection and you turn it into a milder one. ... The vaccines keep us out of the emergency room, prevent hospitalizations, ICU admissions and death,” says Schaffner.
A secondary effect of the vaccine is it helps reduce the burden of influenza on health care systems during fall and winter, Ko added.
Can I get my flu shot and COVID-19 booster at the same time?
Yes, you can and should get your flu shot and COVID-19 booster at the same time, says Schaffner.
After a summer surge of COVID-19 in the U.S. driven by the FLiRT variants, officials are encouraging Americans to get the updated COVID-19 vaccine this fall.
The CDC recommends everyone ages 6 months and older get the COVID-19 vaccine, which has been reformulated to better protect against the highly contagious strains circulating, TODAY.com previously reported.
Experts recommend getting both shots during one appointment for convenience. “There isn’t any scientific evidence that tells you that you have to space them out,” said Ko. However, you may want to get the shots in different arms.
“I encourage people to get both at the same time ... especially if you’re in one of the high-risk groups for COVID-19 or influenza ... whether it be the elderly, the immunocompromised, people with secondary medical conditions,” said Pekosz.
In addition to the COVID-19 booster, an RSV vaccine is also available for pregnant people (to prevent RSV in newborns), adults ages 75 and older, and high-risk adults ages 60 to 74.
All three of these vaccines — for flu, COVID and RSV — can help prevent serious disease and complications, says Schaffner.
How to prepare for flu season
In addition to getting vaccinated, you can take everyday actions to prevent the spread of flu and other respiratory viruses.
These include staying home when sick, avoiding contact with sick people, covering coughs and sneezes, washing your hands and disinfecting contaminated, shared surfaces. Influenza viruses are highly contagious and spread from person to person through respiratory droplets, per the CDC.
If you do get sick with the flu, it's important to monitor symptoms. Flu can range from mild to severe, but most people will recover without needing medical care or treatment, the experts note.
Flu symptoms
The most common flu symptoms include:
Fever
Body aches
Headache
Fatigue
Chills
Cough
Sore throat
Stuffy nose
The CDC recommends staying home for at least 24 hours after your fever is gone (except to seek medical attention) and to contact your health care provider if you are concerned, feeling very sick, or in a high-risk group (over 65, immunocompromised, pregnant, etc.).
There are also flu antivirals available, such as Tamiflu, which require a prescription from a doctor. "Those work really well in terms of keeping people out of the hospital and limiting disease severity," said Pekosz, adding that antivirals are particularly important for high-risk groups.
Ultimately, the goal is to prevent people from getting sick in the first place. “When we’re thinking about public health, the most efficient thing is to prevent disease rather than wait until people are sick and they need to get treated,” Ko said.
This article was originally published on TODAY.com