Can You Get Two Flu Shots in the Same Season?

Two syringes on a pale blue background.


Key Takeaways

  • Most people only need one annual influenza vaccine to be protected for the entire season.
  • Flu shots don’t really have boosters like other vaccines do, but there are some cases where a person might need a second shot in the same flu season. For example, children ages 6 months to 8 years who are getting flu shots for the first time. They will need two doses of flu vaccine that are spaced four weeks apart.
  • Experts are predicting a more severe cold and flu season this year, which is why getting your flu shot as soon as possible is important.

With a longer and more severe cold and flu season expected this year, many are wondering if one dose of the influenza vaccine will be enough to ward off severe illness and dangerous respiratory complications. 

With a lot of talk about extra vaccine doses and booster shots for COVID-19, you might wonder if getting two flu shots would offer more protection—or if it’s even possible to get more than one flu shot in the same season.

Just one flu shot a year is recommended (and enough) for most people, but there are exceptions—for example, kids who are getting a flu shot for the first time.

Roshni Mathew, MD, co-medical director of Infection Prevention & Control and pediatric infectious diseases physician at Stanford Medicine Children’s Health, told Verywell that children ages 6 months to 8 years old who “have not previously received a total of two or more doses in their lives need two doses, separated at least by four weeks.”

According to Mathew, “everyone else only needs to get a single influenza vaccine for the season.”

How Well Does One Flu Shot Work?

Each February, the United States works with the World Health Organization (WHO) to determine the formulation of the flu vaccine for the upcoming influenza season. The goal is to closely match the same viruses that are currently circulating and causing illness.

All U.S. flu vaccines protect against type A and B viruses. This includes a flu A(H1) virus, a flu A(H3) virus, a flu B/Yamagata lineage virus, and a flu B/Victoria lineage virus. Flu vaccine components are determined based on current international data, including:

  • Which flu viruses are currently making people sick
  • How much the viruses are spreading
  • The effectiveness of the previous season’s vaccines against the virus
  • The ability of the vaccine to provide cross-protection against multiple flu virus types

In some years, flu shots will work pretty well. In others, not so much. A flu vaccine’s effectiveness is affected by a number of factors, including:

  • The age and health of the person getting vaccinated
  • Which strain of flu virus is going around—e.g., the vaccines tend to offer the most protection against influenza B and influenza A (H1N1) viruses and less against influenza A (H3N2) viruses

Would Two Flu Shots Ever Be Recommended for Adults?

While kids benefit from two flu shots, there is not enough evidence to show that it would be helpful for any other groups to get a second dose.

Some studies in adults with compromised immune systems (like organ transplant recipients) have looked at whether getting a second flu shot might be helpful, but more research is needed before the recommendation would be changed.

Currently, the Centers for Disease Control and Prevention (CDC) states that for adults, “studies have not shown a benefit from getting more than one dose of vaccine during the same influenza season, even among elderly persons with weakened immune systems.”

What If I Get Two Flu Shots By Mistake?

If you accidentally get two flu vaccines by mistake, don’t panic. Getting a double dose is not dangerous, but it’s also not going to be more helpful than getting one.

How Long Does Flu Shot Protection Last?

A flu shot that works well is key to combating a severe flu season, but the length of immunity provided by each annual dose is another key aspect.

According to experts, flu vaccine immunity wanes over time but typically provides protection for five to six months. However, this timeframe depends on different factors like a person’s age and the strain of flu virus that’s going around.

Buddy Creech, MD

We know that vaccine effectiveness wanes through the season, with some estimating an approximate 5% loss each month following vaccination.

— Buddy Creech, MD

“The length of the influenza season is, indeed, relevant to our strategy for vaccination,” Buddy Creech, MD, MPH, a professor and chair in the Department of Pediatrics at the Vanderbilt University Medical Center and the director of the Vanderbilt Vaccine Research Program, told Verywell. “We know that vaccine effectiveness wanes through the season, with some estimating an approximate 5% loss each month following vaccination.”

That said, Creech added that these numbers are challenging to come by.

“[I] think it’s fair to say that the longer we go after vaccination, the less immunity we have.”

Reasons You Might Want to Get a Flu Shot Early

Some people may want to get their yearly flu shot a little sooner. For example:

  • Travelers who missed vaccination in the previous winter or fall
  • Children younger than age 9 who needed two doses of the flu vaccine but did not get their second dose early in the season
  • People who may not be able to get vaccinated later in the season
  • People in the third trimester of pregnancy

Despite waning immunity over time, the CDC still says that one flu shot is enough to get the general population through an entire flu season. 

“This is part of the reason CDC suggested that older individuals get vaccinated in October rather than being first in line to get them in July or August,” said Creech. “We do not fully know the characteristics of waning immunity in children, but it is clear that vaccinating in the fall protects children through the influenza season, even when it extends into the very late spring.”

Experts suggest people get their annual flu shot in September or at least by the end of October. The flu vaccine is offered as long as the flu virus is circulating in the community, but the U.S. flu season tends to peak in January and then taper down in the spring. 

Which Flu Shot Should You Get?

The CDC recommends that everyone over the age of 6 months get their flu shot. The flu vaccines for the season are available at providers’ offices, pharmacies, and even grocery stores. If you’re over the age of 65, the CDC recommends that you get one of the three high-dose vaccines:

  • Fluzone High-Dose Quadrivalent vaccine 
  • Flublok Quadrivalent recombinant flu vaccine
  • Fluad Quadrivalent adjuvanted flu vaccine

While you most likely only need to get one flu shot per flu season, timing matters. Remember that it takes about two weeks after you get vaccinated for immunity to kick in.

What This Means For You

Annual influenza vaccines are recommended for everyone aged 6 months and older. The only group that needs more than one flu shot per season (two doses spaced four weeks apart) is kids between the ages of 6 months and 8 years old who haven’t gotten a flu shot before.

People over the age of 65 should get one of three high-dose flu vaccines available to ensure they get the best protection. Getting your flu shot in the months of September and October helps make sure you have protection through peak flu season into the spring.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. How influenza (flu) vaccines are made.

  2. Centers for Disease Control and Prevention. Selecting viruses for the seasonal influenza vaccine.

  3. Centers for Disease Control and Prevention. Vaccine effectiveness: how well do flu vaccines work?.

  4. Bosaeed M, Kumar D. Seasonal influenza vaccine in immunocompromised personsHum Vaccin Immunother. 2018;14(6):1311-1322. doi:10.1080/21645515.2018.1445446

  5. Cordero E, Roca-Oporto C, Bulnes-Ramos A, et al. Two doses of inactivated influenza vaccine improve immune response in solid organ transplant recipients: results of TRANSGRIPE 1-2, a randomized controlled clinical trialClin Infect Dis. 2017;64(7):829-838. doi:10.1093/cid/ciw855

  6. Immunization Action Coalition. What to do if the wrong dose of a vaccine is administered.

  7. Immunization Action Coalition. Ask the experts: influenza.

  8. Centers for Disease Control and Prevention. Frequently asked influenza (flu) questions: 2022-2023 season.

  9. Centers for Disease Control and Prevention. Inactivated influenza VIS.

  10. Centers for Disease Control and Prevention. Who needs a flu vaccine.

By Amy Isler, RN, MSN, CSN
Amy Isler, RN, MSN, CSN, is a registered nurse with over six years of patient experience. She is a credentialed school nurse in California.