The flu shot: 8 things you should know

Flu season brings the same annual question: should you get the flu shot? The answer, for almost everyone, is yes. Here are eight things that will help you understand what the vaccine does, why it matters, and how to make it easy.

1. You need a new flu shot every year

The influenza virus mutates constantly. Each year, the World Health Organization and the FDA analyze circulating strains and update the vaccine formulation to match the viruses most likely to spread that season.¹ Immunity from last year's shot provides little or no protection against this season's strains, which is why annual vaccination is essential—not optional.

For the 2025–2026 season, the FDA selected updated influenza A (H1N1 and H3N2) and influenza B components based on global surveillance data.²

2. The flu shot cannot give you the flu

This is one of the most persistent vaccine myths. Standard flu shots use inactivated (killed) influenza virus or, in recombinant vaccines, flu proteins produced without any virus at all. Neither can cause influenza infection.³

If you feel under the weather in the days after vaccination, you are likely experiencing a mild immune response—not the flu. Arm soreness, low-grade fever, or fatigue are signs your immune system is building protection, and they resolve within 1–2 days.

3. It's recommended for nearly everyone

The CDC recommends annual influenza vaccination for everyone 6 months and older, with rare exceptions.⁴ The following groups have especially strong reasons to vaccinate:

• Adults 65 and older (higher-dose or adjuvanted vaccines are preferred)
• Pregnant women (the shot protects both mother and newborn)
• Children 6 months through 8 years (may need two doses their first flu season)
• People with chronic health conditions: asthma, heart disease, diabetes, obesity, or weakened immune systems
• Healthcare workers and caregivers for infants or elderly adults

The only people who should not receive the standard flu shot are infants under 6 months and those with a documented history of severe allergic reaction to a flu vaccine ingredient. Egg-free formulations are available for people with egg allergies.

4. Timing matters—but later is still better than never

The optimal time to get vaccinated is by the end of October, giving your immune system two weeks to build full protection before flu activity typically picks up in November and December.⁵ That said:

• Flu season can extend into March or April, so vaccinating in November, December, or even January still provides real protection.
• Do not skip the vaccine because you missed the October window.
• Getting vaccinated too early (July or August) may result in waning immunity later in the season for older adults; aim for September–October.

5. Side effects are normal and brief

Common side effects from the flu shot include:⁶

• Soreness, redness, or mild swelling at the injection site
• Low-grade fever (below 101°F)
• Headache or muscle aches
• Fatigue

These effects typically appear within a few hours of vaccination and resolve within one to two days. Serious allergic reactions (anaphylaxis) are rare—occurring in roughly 1–2 cases per million doses—and are why clinics ask you to wait 15 minutes after receiving the shot.

6. It reduces serious complications, not just illness

Even in seasons when vaccine effectiveness against all flu illness is moderate (40–60%), vaccination consistently delivers stronger benefits for severe outcomes:⁷

• Reduces flu-related hospitalization in adults by 40% or more
• Reduces flu deaths in older adults
• Reduces flu-related ICU admissions
• Protects pregnant women from flu-related pregnancy complications
• Provides newborns with maternal antibodies during their first months of life

When you vaccinate, you also protect people around you who cannot be vaccinated—infants, immunocompromised individuals, and others who depend on community immunity.

7. There are several vaccine types to choose from

Not all flu vaccines are the same. Options include:⁸

• Standard-dose inactivated flu shot: The most common option, approved for adults and children 6 months and older.
• High-dose flu shot (Fluzone High-Dose): Contains four times the antigen of standard vaccines; preferred for adults 65 and older because it produces a stronger immune response.
• Adjuvanted flu shot (Fluad): Contains an immune-boosting ingredient (MF59); also preferred for adults 65 and older.
• Recombinant flu shot (Flublok): Made without eggs, suitable for people with egg allergies.
• Nasal spray vaccine (FluMist): A live attenuated vaccine for healthy, non-pregnant individuals ages 2–49. Not recommended for immunocompromised individuals or pregnant women.

Your provider or pharmacist can help you choose the right formulation based on your age and health history.

8. Getting vaccinated is easier than ever

You do not need a scheduled appointment with your primary care doctor to get a flu shot. Convenient options include:

• Urgent care centers: Most offer flu vaccines walk-in, with minimal wait times and evening or weekend hours.
• Pharmacies: Chain pharmacies like CVS, Walgreens, and Rite Aid offer flu vaccines without appointments.
• Retail clinics: In-store health clinics provide fast, low-cost vaccinations.
• Your employer or school: Many workplaces and universities offer free on-site flu vaccine clinics.

Most private insurance plans, Medicare, and Medicaid cover flu vaccines at no cost under preventive care benefits. Use Solv to find an urgent care or walk-in clinic near you that offers flu vaccinations.