Flu Shot Questions Answered: Timing, Side Effects, Best Shot for 65+ and the 2026-2027 Vaccine
Written by Naurah Gaspard, DNP, FNP-C, FNP-BC · Medically reviewed by Cherlie Joseph, MSN, FNP-BC · Updated November 2026
Adults should get a flu shot every year, ideally in September or October, but getting one later in the season still helps while flu is spreading. If you're 65 or older, a high-dose, adjuvanted or recombinant flu vaccine is preferred. A flu shot cannot give you the flu; a sore arm or a day of feeling tired is the most common side effect.
In this guide
What's new in the 2026-2027 flu vaccine
Each spring, the FDA picks the virus strains for the next season's vaccine. For 2026-2027, all three strains were updated from last year, including a new H3N2 strain chosen to better match the H3N2 subclade K virus that spread widely during the 2025-2026 season. Key points:
- All US flu vaccines this season are trivalent, meaning they protect against three strains: an H1N1, an H3N2 and a B/Victoria virus.
- About 99% of the projected supply contains no thimerosal preservative.
- Roughly a quarter of the supply is made without eggs (cell-based or recombinant).
Because flu viruses change and protection fades over months, last year's shot won't fully protect you this year.
When to get your flu shot
September and October are ideal for most adults, so you're protected before flu peaks. It takes about two weeks after the shot for your body to build protection. If you missed that window, it's not too late: the CDC recommends vaccinating as long as flu is circulating, which in Florida can run into spring.
A few timing tips:
- Sick right now? A mild cold isn't a reason to wait. With a moderate or severe illness or fever, wait until you feel better.
- Other vaccines: You can usually get your flu shot at the same visit as a COVID or RSV vaccine. Ask your pharmacist what fits your situation.
- Very early shots: Adults 65 and older are generally advised not to get vaccinated in July or August, since protection can wane before the end of the season.
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For most adults 18 to 64, any age-appropriate flu vaccine is fine; there's no need to hunt for a specific brand. Adults 65 and older get stronger protection from one of three preferred options when available:
| Vaccine type | Who it's for | Notes |
|---|---|---|
| Standard-dose shot | Most adults under 65 | Egg-based or cell-based |
| High-dose shot | Preferred at 65+ | More antigen for an older immune system |
| Adjuvanted shot | Preferred at 65+ | Contains an ingredient that boosts response |
| Recombinant shot | Adults 18+, preferred at 65+ | Made without eggs |
| Nasal spray (FluMist) | Healthy, non-pregnant people up to age 49 | Live, weakened virus; not for weakened immune systems |
If the preferred vaccine for your age isn't in stock, don't skip the shot; any age-appropriate flu vaccine is better than none.
Side effects and safety
Flu shots contain inactivated virus or a single viral protein, so they can't cause the flu. Common side effects last a day or two:
- Soreness, redness or swelling where the shot was given
- Low-grade fever, headache or muscle aches
- Tiredness or mild nausea
High-dose and adjuvanted vaccines can cause a bit more arm soreness. Serious allergic reactions are rare and usually happen within minutes, which is why pharmacies ask you to wait briefly after the shot. Egg allergy is no longer a reason to avoid the flu shot: people with an egg allergy can receive any age-appropriate flu vaccine. If you've had a severe reaction to a flu vaccine before, or Guillain-Barré syndrome within 6 weeks of one, talk with a provider first.
Pregnancy, chronic conditions and cost
Flu shots are recommended during pregnancy at any trimester and help protect the baby for the first months of life. People with diabetes, heart disease, asthma, COPD or kidney disease benefit the most, because flu is more likely to put them in the hospital.
Most insurance plans, including Medicare Part B, cover the flu shot with no copay at in-network pharmacies. Without insurance, cash prices at major pharmacies typically run about $40 to $90 depending on the vaccine; prices change, so check with your pharmacy. Florida county health departments also offer flu vaccines.
If you do get the flu, a prescription antiviral like Tamiflu or Xofluza works best when started within 48 hours of symptoms, so reach out early.
Get in-person care or call 911 if you have:
- Signs of a severe allergic reaction after a shot: swelling of the face or throat, hives, trouble breathing, fast heartbeat or dizziness
- Trouble breathing or chest pain during a flu illness
- New confusion or trouble staying awake
- Flu symptoms that improve, then return with fever and a worse cough
Frequently asked questions
Can the flu shot give you the flu?
No. Flu shots contain inactivated virus or a single protein, which can't cause infection. Some people feel achy or tired for a day as the immune system responds, and some catch a different virus around the same time, which can feel like the shot caused it.
Is it too late to get a flu shot in December or January?
No. The CDC recommends flu vaccination as long as flu viruses are circulating. In Florida, flu can spread into spring, so a shot in winter still offers protection.
What is the best flu shot for seniors?
For adults 65 and older, the CDC prefers a high-dose, adjuvanted or recombinant flu vaccine when available. If none of those is available, any age-appropriate flu vaccine is better than skipping it.
Sources
Keep reading
- Flu Treatment: Tamiflu vs Xofluza
- How Long Is the Flu Contagious?
- RSV in Adults: Symptoms, Risk and the RSV Vaccine
- Browse all conditions and treatments A to Z
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Naurah Gaspard, DNP, FNP-C, FNP-BC
Board-certified family nurse practitioner licensed in Florida, New Mexico, Oregon and Washington, caring for adults online at OurTopClinic. Meet our providers.
This article is for general education and is not a substitute for medical advice. Treatment, including any prescription, is decided by a licensed provider after reviewing your health history. OurTopClinic is not for emergencies; if you have a medical emergency, call 911. OurTopClinic serves adults located in Florida, New Mexico, Oregon and Washington. Learn more at ourtopclinic.com.
