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Prevention & screening

Do You Really Need a Flu Shot Every Year? Yes — Here Is Why

Yes. The CDC and World Health Organization recommend a flu shot every year for nearly everyone 6 months and older. Annual vaccination is needed for two reasons: influenza viruses change each season, and the immunity the vaccine produces fades over time. Vaccinating each fall is the most effective way to lower flu risk.

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Why do flu viruses require a new vaccine every year?

Influenza viruses mutate more rapidly than most respiratory viruses — a process called antigenic drift. Each year, international surveillance networks track which strains are circulating globally, and the WHO recommends an updated vaccine composition designed to match strains expected to dominate the coming season 1.

Last year's shot targeted last year's strains. This year's circulating virus may be meaningfully different. A flu shot from two or three seasons ago may offer little protection against the strains currently in circulation.

Why does flu vaccine immunity fade even if the virus does not change?

Even if the circulating strain were unchanged, immunity from the flu shot wanes over the months following vaccination. Studies have found that protection is highest in the first months after the shot and declines by the end of flu season. Annual vaccination renews that protection at the right time — typically in early fall — so immunity is at its peak during the months when flu circulates most actively 12.

Who benefits most from the annual flu vaccine?

While annual vaccination benefits nearly everyone, it is especially important for 12:

  • Adults 65 and older — flu can cause serious complications; high-dose or adjuvanted vaccine formulations are specifically recommended for this group because standard-dose vaccines can produce a weaker immune response in older adults
  • Children under 5, particularly those under 2
  • Pregnant individuals — flu during pregnancy carries higher risk of serious complications, and vaccination also passes some protective antibodies to the newborn
  • People with chronic conditions: heart disease, lung disease, diabetes, kidney disease, or weakened immune systems
  • People who live with or regularly care for high-risk individuals
  • Healthcare workers — both for personal protection and to avoid transmitting flu to vulnerable patients

Common concerns about the flu shot, answered plainly

"The flu shot gave me the flu." The injected flu vaccine contains inactivated (killed) virus and cannot cause flu infection. Some people experience achiness or a low-grade fever for a day or two — this is the immune system responding, not an infection.

"I got the shot and still got sick." This happens. No vaccine is 100% effective. The vaccine reduces the risk of infection and — importantly — significantly reduces the severity and risk of complications even when breakthrough infection occurs. Partial protection is still meaningful protection.

"I'm healthy — I don't need it." Healthy adults can and do develop severe flu. They also transmit it to those who cannot fight it as effectively. The vaccine protects you and reduces your chance of passing illness to more vulnerable people around you.

When is the best time to get vaccinated?

The ACIP recommends getting vaccinated ideally by the end of October 1. September and October are generally better than waiting until November or later. That said, getting vaccinated in November, December, or even later in the season is still worthwhile — flu can circulate well into spring. It takes about two weeks after vaccination for full immunity to develop.

Are there special considerations for certain groups?

Severe egg allergy: Most flu vaccines are grown in eggs. People with severe egg allergies can still receive the flu vaccine — recombinant and cell-based formulations do not use eggs — but should discuss the right product with their clinician 1.

Pregnancy: Flu vaccination is strongly recommended during any trimester. It protects both the pregnant person (who is at higher risk of severe disease) and provides some protection to the newborn in early life 1.

Immunocompromised individuals: Should receive the inactivated (injected) vaccine rather than the live attenuated nasal spray. The immune response may be somewhat less robust — a clinician can advise on timing and formulation.

Age 65 and older: High-dose, adjuvanted, or recombinant vaccine formulations are specifically designed and recommended for this group and are available at most pharmacies and clinics 12.

Common questions

If I got a flu shot last year, do I really need another one this year?

Yes. Both the virus and your immunity change year to year. Last season's vaccine targeted different strains, and whatever immunity it produced has likely waned. Getting vaccinated each fall is the recommendation for everyone 6 months and older.

Can I get my flu shot and COVID-19 or other vaccines at the same visit?

Generally yes. The flu shot can be given at the same visit as most other vaccines. Your clinician or pharmacist can confirm based on your specific situation and the vaccines you need.

Is the nasal spray flu vaccine as effective as the shot?

The nasal spray (FluMist) contains a weakened live virus and is approved for healthy, non-pregnant people aged 2 through 49. Its effectiveness compared to the injected vaccine varies by year and strain type. It is a reasonable alternative for people who strongly prefer not to receive an injection, but the injected vaccine is recommended for most high-risk groups.

I have an egg allergy. Which flu vaccine should I get?

People with egg allergies, even severe ones, can safely receive flu vaccines. Those with a history of severe allergic reactions to eggs should receive the vaccine in a medical setting and be observed afterward. Recombinant or cell-based flu vaccines contain no egg protein and are an alternative — your clinician or pharmacist can guide you to the right formulation.

Is there a stronger flu shot for people over 65?

Yes. High-dose, adjuvanted (Fluad), and recombinant (Flublok) formulations are specifically available for adults 65 and older and are recommended by the ACIP. They produce a stronger immune response in older adults compared to standard-dose vaccines.

Talk to a clinician

Nina Osei, NP — Nurse Practitioner

checkups, refills & skin. Gale can match you with a licensed clinician for a visit.

Find care →

Signs of serious flu that need prompt care

  • —High fever above 103 degrees F (39.4 degrees C) lasting more than a few days
  • —Difficulty breathing or shortness of breath
  • —Chest pain or pressure
  • —Confusion or altered mental status
  • —Severe vomiting with inability to keep fluids down
  • —In a child: no wet diapers, no tears, extreme listlessness

If you or someone with you has trouble breathing, chest pain, severe confusion, or cannot stay awake, call 911 or go to the emergency department immediately.

This article provides general health education only and is not a personalized medical recommendation. Speak with a licensed clinician or pharmacist about the right flu vaccine formulation for your age, health status, and any allergies.

References

  1. 1.Grohskopf LA, Blanton LH, Ferdinands JM, 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. MMWR Recommendations and Reports. link ✓Annual influenza vaccination recommended for all persons ≥6 months; vaccination ideally by end of October; high-dose, adjuvanted, or recombinant formulations preferred for adults 65+; pregnancy recommendation; egg-allergy guidance; annual composition updated by WHO surveillance
  2. 2.Wodi AP, Issa AN, Moser CA, Cineas S (2025). Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older — United States, 2025. MMWR Morb Mortal Wkly Rep. doi:10.15585/mmwr.mm7402a3 ✓ACIP adult immunization schedule including annual influenza vaccination, high-dose formulations for adults 65+, and egg-allergy guidance

2 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.