Key takeaways:
The yearly flu shot saves lives and prevents serious illness.
You need to get a new flu shot each year to stay protected from changes to the flu virus.
The flu shot protects you and the people close to you who may be at risk for serious complications from the flu.
Save on related medications
The flu (influenza) is a respiratory virus that circulates each year, typically in the colder months that make up flu season. It causes mild illness for some people, but it can cause serious illness and death for others.
Getting a yearly flu shot is the best way to protect yourself from the flu. Every year it saves lives. It does this by preventing people from catching the flu and by making the illness less serious for people who do get sick.
The flu virus changes (mutates) easily, and different versions (strains) of the flu virus circulate yearly. Also, protection from the flu shot wanes over time. That’s why just about everyone should get an updated flu shot every year.
Search and compare options
Should you get a flu shot every year?
Yes, experts recommend getting the flu vaccine every year. The influenza virus spreads easily through communities. It floats through the air in water droplets, and it sticks to surfaces you might touch. If the virus gets inside your body, it can make you sick.
Part of the flu virus stays the same every year. But other parts of the virus change as the virus spreads from person to person.
Since the flu virus changes all the time, the flu shot needs to change too. This means that the flu shot you got last year won’t protect you against this year’s flu virus.
Plus, the immune defenses (antibodies) your body makes in response to the flu vaccine weaken with time. So, even if the flu virus strains didn’t change from year to year, you would still need regular flu vaccine boosters to keep your defenses strong.
How does the flu vaccine work?
Vaccines work by teaching your immune system how to respond when you’re exposed to a pathogen (like the influenza virus). Traditional vaccines do this by introducing a weak or inactive form of a pathogen into the body. Newer vaccines use recombinant technology to create the pathogen. Regardless of how it’s made, the flu shot typically includes influenza A and B, which are the types that make people sick.
After the vaccine, the immune system recognizes the virus and gets rid of it. It then remembers how to do this again if you’re exposed to it later in the season. So, if you come into contact with the flu, you’re less likely to get sick with it because your immune system takes care of it. And, even if you do get sick, you’re less likely to develop serious symptoms or complications.
Does the flu shot actually work? Yes, the flu vaccine is effective and the best way to protect yourself from the flu.
Can kids get a flu shot if they have a cold? Yes, most kids can still get a flu shot if they have a mild illness like a cold. A pediatrician shares the details.
Where to get a flu test: A flu test is a sure way to know whether you have the flu. Here’s where to get one now.
What flu vaccine options are available?
Each year, there are several flu vaccine options available. Most are given as an injection (shot), and anyone 6 months or older can get the flu shot. Pharmacies and medical clinics generally carry a limited number of vaccine brands. So, if you’re interested in a particular vaccine, it’s best to call ahead. But there isn’t usually a difference in their effectiveness.
Another option is FluMist, which is a nasal spray. This vaccine contains a live, weakened virus. It’s available for anyone ages 2 to 49. But you shouldn’t take this vaccine if you’re pregnant or have certain medical conditions.
People ages 65 and older may opt for the high-dose flu shot. This is because older adults are at higher risk of complications from the flu, like pneumonia requiring hospitalization. High-dose flu vaccines are more effective than standard-dose vaccines for this population. But if one of the high-dose flu shots isn’t available, it’s OK to get a regular flu shot.
How effective are flu shots?
The flu shot is typically about 40% to 60% effective at preventing flu infections. But exactly how effective the flu shot is in a given year depends on how well the circulating flu virus matches the vaccine.
Why does the flu shot’s effectiveness vary so much?
The effectiveness of the flu shot has a bit to do with timing and educated guessing. This is because public health scientists and flu virus researchers have to predict 6 months in advance what they think the next year’s flu virus will look like.
You might be wondering how scientists make these predictions. Around February of each year, experts with the World Health Organization (WHO) review data from the last flu season. Based on this info, they make an educated guess about which strains are most likely to circulate during the next flu season.
These experts then recommend which strains should be covered in the new flu shot. This gives the flu shot manufacturers the 6 months they need to prepare the new flu shot. In late summer, the seasonal flu shot is typically ready to be given out.
In some seasons, the prediction of the strains matches the reality of the strains spreading in the community. When this happens, the vaccine is very effective. In other seasons, the flu virus may change, and strains that aren’t covered by the vaccine may cause the most illness. In these seasons, the flu shot is less effective.
Quiz: Test your flu shot knowledge
How long does a flu shot last?
This is unclear, and research is ongoing. In one study of younger adults (ages 18 to 49), flu antibodies decreased slowly over 18 months after they got their shots. Another study of the same age group showed that antibody levels remained high enough to be effective throughout the whole flu season — or 5 to 6 months after vaccination. Similar research supports several months of protection in older adults as well.
When is the best time to get a flu shot?
You should get the flu shot each year at least 2 weeks before the flu virus starts spreading in your community. Flu season is typically October to May in the Northern Hemisphere (where the U.S. is located). So, the flu shot usually becomes available around September of each year.
The CDC recommends getting the flu vaccine no earlier than September and no later than the end of October.
Basically, you want to time it just right so that you’re fully vaccinated when the flu virus starts to circulate. But you don’t want to be too early so that your immunity runs out before the end of the flu season (which can last as late as May).
You can still get the flu in summer, but this is less likely to happen. Remember, it’s almost never too late to get a flu shot.
Who should not get a yearly flu shot?
Almost everyone (except infants) should get a yearly flu shot. The only reason not to get the standard flu shot is if you’ve had a severe reaction to the flu shot or any components of the flu shot in the past. If you’ve had Guillain-Barré syndrome in the past, speak with a healthcare professional first.
There are other versions of the flu vaccine (like the flu nasal spray vaccine) that have different guidelines. Check out our article on flu vaccine options and ingredients.
Frequently asked questions
The flu shot can cause some short-lived side effects that can make you feel sick. This is a normal reaction. It’s a sign that your immune system is making antibodies to help prevent future infections. But you can't get the flu from the flu vaccine. Some people can have an allergic reaction to the flu shot, but this is rare.
Yes, you can get a flu shot if you have a mild illness, like a common cold or other upper respiratory tract infection. But if you aren’t sure what’s causing your symptoms, it’s best to check with your primary care provider. They may recommend that you reschedule your flu shot until your symptoms have improved.
No, a regular flu shot doesn’t give you protection against bird flu viruses. For now, the best way to protect against bird flu is to avoid coming into contact with wild birds and to thoroughly cook poultry before eating it. Ongoing work on a vaccine against bird flu was recently canceled by the Department of Health and Human Services.
Hopefully not. Research is ongoing to create a universal flu shot, and clinical trials are due to begin in 2026. This universal flu vaccine would, in theory, help your body create antibodies against the part of the flu virus that doesn’t change every year.
Right now, yearly vaccines target those proteins on the surface of the flu virus that change throughout the flu season. A new universal vaccine would protect you against current strains of the flu virus as well as future mutations of the flu virus.
Healthy people should get vaccinated against the flu vaccine every year. That’s because anyone can get seriously ill from the flu. And some groups have a higher risk than others.
But the flu vaccine helps prevent serious illness and death from the flu in all people who get vaccinated. It also reduces the spread of the flu to people who can’t get vaccinated. The more people who get the flu vaccine, the more everyone in our communities is protected.
The flu shot can cause some short-lived side effects that can make you feel sick. This is a normal reaction. It’s a sign that your immune system is making antibodies to help prevent future infections. But you can't get the flu from the flu vaccine. Some people can have an allergic reaction to the flu shot, but this is rare.
Yes, you can get a flu shot if you have a mild illness, like a common cold or other upper respiratory tract infection. But if you aren’t sure what’s causing your symptoms, it’s best to check with your primary care provider. They may recommend that you reschedule your flu shot until your symptoms have improved.
No, a regular flu shot doesn’t give you protection against bird flu viruses. For now, the best way to protect against bird flu is to avoid coming into contact with wild birds and to thoroughly cook poultry before eating it. Ongoing work on a vaccine against bird flu was recently canceled by the Department of Health and Human Services.
Hopefully not. Research is ongoing to create a universal flu shot, and clinical trials are due to begin in 2026. This universal flu vaccine would, in theory, help your body create antibodies against the part of the flu virus that doesn’t change every year.
Right now, yearly vaccines target those proteins on the surface of the flu virus that change throughout the flu season. A new universal vaccine would protect you against current strains of the flu virus as well as future mutations of the flu virus.
Healthy people should get vaccinated against the flu vaccine every year. That’s because anyone can get seriously ill from the flu. And some groups have a higher risk than others.
But the flu vaccine helps prevent serious illness and death from the flu in all people who get vaccinated. It also reduces the spread of the flu to people who can’t get vaccinated. The more people who get the flu vaccine, the more everyone in our communities is protected.
The bottom line
The yearly flu shot is safe and effective, and it saves lives. It also prevents you and the people around you from suffering from unnecessary illness. Everyone ages 6 months and older should get the flu shot every year.
Why trust our experts?
References
Adams, K., et al. (2021). A literature review of severity scores for adults with influenza or community-acquired pneumonia - implications for influenza vaccines and therapeutics. Human Vaccines and Immunotherapeutics.
Centers for Disease Control and Prevention. (2020). Who should NOT get vaccinated with these vaccines?
Centers for Disease Control and Prevention. (2022). Live attenuated influenza vaccine [LAIV] (the nasal spray flu vaccine).
Centers for Disease Control and Prevention. (2024). Benefits of the flu vaccine.
Centers for Disease Control and Prevention. (2024). Effectiveness against different flu viruses.
Centers for Disease Control and Prevention. (2024). Factors influencing flu vaccine effectiveness.
Centers for Disease Control and Prevention. (2024). Key facts about seasonal flu vaccine.
Centers for Disease Control and Prevention. (2024). Recombinant influenza (flu) vaccine.
Centers for Disease Control and Prevention. (2024). Who needs a flu vaccine.
Centers for Disease Control and Prevention. (2025). Preventing bird flu infections.
Grohskopf, L. A., et al. (2024). Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2024–25 influenza season. Morbidity and Mortality Weekly Report.
Immunize.org. (2024). Ask the experts: Influenza.
National Institutes of Health. (2025). HHS, NIH launch next-generation universal vaccine platform for pandemic-prone viruses.
Petrie, J. G., et al. (2015). Persistence of antibodies to influenza hemagglutinin and neuraminidase following one or two years of influenza vaccination. The Journal of Infectious Diseases.
Petrie, J. G., et al. (2016). Modest waning of influenza vaccine efficacy and antibody titers during the 2007-2008 influenza season. The Journal of Infectious Diseases.
Sautto, G. A., et al. (2018). Towards a universal influenza vaccine: Different approaches for one goal. Virology Journal.
Skowronski, D. M., et al. (2008). Rapid decline of influenza vaccine—induced antibody in the elderly: Is it real, or is it relevant? The Journal of Infectious Diseases.
Stein, R., et al. (2025). Trump administration cancels plans to develop a bird flu vaccine. National Public Radio.
U.S. Food and Drug Administration. (2025). Influenza vaccine composition for the 2025-2026 U.S. influenza season.
World Health Organization. (n.d.). Global Influenza Surveillance and Response System (GISRS).
