Quick answer: No, the flu shot cannot give you the flu. The injected vaccine contains no live virus. The most common side effects are a sore arm, mild headache, tiredness or a low fever that usually fade within 1 to 2 days. Serious reactions are very rare. If you feel sick after a flu shot, it is usually a short-lived immune response or a different virus you caught around the same time.
Myths keep many people from getting a flu shot every year. Here’s what the science actually says about side effects, and what’s normal versus what needs attention.
Common side effects (normal and short-lived)
- Soreness, redness or swelling where the shot was given
- Headache
- Low-grade fever
- Muscle aches
- Tiredness or mild nausea
These are signs your immune system is building protection. They usually start within a day and go away in 1 to 2 days. The nasal spray vaccine can also cause a runny nose or sore throat.
How to ease a sore arm
- Keep moving the arm after your shot
- Apply a cool compress
- Take an over-the-counter pain reliever if your provider says it’s okay
Rare but serious reactions
Severe allergic reactions are very rare and usually happen within minutes to hours. Call 911 for hives with swelling of the face or throat, trouble breathing, a fast heartbeat, dizziness or weakness. Guillain-Barré syndrome has been linked to flu vaccines in about 1 or 2 cases per million doses, a risk far smaller than the risk of serious complications from the flu itself.
Flu shot myths vs. facts
| Myth | Fact |
|---|---|
| The flu shot gives you the flu | Flu shots contain inactivated virus or a single protein. They cannot cause flu infection. |
| I got the flu shot last year, so I’m covered | Protection fades and strains change. You need a new shot every season. |
| The flu is just a bad cold | Flu sends hundreds of thousands of Americans to the hospital each year. See flu complications. |
| Healthy people don’t need it | Healthy adults and kids can get very sick, and can spread flu to high-risk family members. |
| People with egg allergies can’t get it | The CDC says people with egg allergies can get any age-appropriate flu vaccine. |
| It’s too late after October | Getting vaccinated later in the season still protects you. |
| Pregnant people should avoid it | The flu shot is recommended during pregnancy and protects the baby after birth. |
Why did I get sick after my flu shot?
- You picked up a cold or another virus around the same time
- You were exposed to flu before the vaccine had 2 weeks to take effect
- The circulating strain didn’t closely match the vaccine
Not sure if it’s flu, a cold or COVID? Read cold, flu or COVID and track flu symptoms day by day. A rapid flu test can give you an answer in one visit.
Frequently asked questions
How long do flu shot side effects last?
Usually 1 to 2 days.
Can I take ibuprofen before my flu shot?
It’s best not to take pain relievers before your shot to prevent side effects. Taking them afterward for discomfort is generally fine.
Is it safe to get the flu and COVID shots together?
Yes. See getting flu and COVID shots on the same day.
Where can I learn more?
See the CDC’s flu vaccine safety information at cdc.gov/flu.
Ready for your shot? Read our flu shot guide.
Get care today at PACS Urgent Care
Walk in or book online at our Alexandria flu clinic (3481 N Beauregard St, open 7 days, 8 AM to 8 PM) or book at our Ruther Glen flu clinic (17067 Merchants Dr, Monday to Friday 8 AM to 8 PM, Saturday and Sunday 9 AM to 5 PM). Prefer to stay home? Start with a telemedicine visit.
This article is general information and is not a substitute for advice from your own clinician.
