6–12 Month Vaccines
Flu Vaccine Side Effects in Babies & Children
The injected flu vaccine can't cause flu — a sore arm, mild fever or tiredness for a day or two is just the immune system at work.
Written and fact-checked by the ParentVibes editorial team against WHO, IAP, CDC and NHS immunisation guidance. Not yet reviewed by a named clinician.
Quick facts
- Usually given
- 6 months onwards, every year
- First year
- 2 doses, 4 weeks apart
- Protects against
- Seasonal influenza
- Typical reaction
- Sore arm ± mild fever or tiredness
- Usually settles in
- 1–2 days
The flu vaccine protects your child against seasonal influenza — an illness that is often far more than a bad cold in young children, sometimes leading to breathing trouble, ear infections or hospital stays. The IAP recommends it from 6 months of age, with two doses four weeks apart in the first year of vaccination and a single dose each year after that.
A yearly flu shot puts off some parents who worry it will make their child unwell. It won't: the injected vaccine contains no live virus, so it cannot cause flu. Any mild fever or achiness afterwards is the sign of a healthy immune response building protection — usually gone within a day or two, and a small trade for avoiding a genuine bout of flu.
What the flu vaccine is
The injected flu vaccine given to children in India is an inactivated (non-live) vaccine — it contains killed or fragmented virus pieces that cannot multiply or cause infection. It teaches the immune system to recognise this season's flu strains.
Flu viruses change from year to year, and the protection from a single shot fades over months. That's why the vaccine is updated and repeated annually — a fresh dose each season keeps your child's protection matched to the strains going around.
Why two doses the first year?
A child getting the flu vaccine for the very first time needs two doses about four weeks apart to build full protection. After that first year, a single yearly dose is enough.
Common flu vaccine side effects
Most children have only mild effects, if any, and they show up soon after the shot rather than days later:
Sore arm or thigh
The injection site is often a little tender, red or slightly swollen for a day or so. This is the most common effect and settles on its own.
Low-grade fever
A mild temperature in the first day or two is common, particularly in younger children, and is a normal sign the immune system is responding.
Tiredness or feeling run-down
Your child may be a bit more tired or less energetic than usual for a day. Extra rest is all that's needed.
Mild body or muscle aches
Some children ache a little or feel generally 'off' for a day or two. This is the immune response at work, not the flu itself.
Reduced appetite or mild fussiness
Babies and toddlers may feed a little less or be fussier on the day of the shot, returning to normal within a day.
Feeling achy isn't the flu
If your child feels mildly achy or feverish after the shot, that's the immune system practising — not an infection. A true flu illness is far heavier and lasts much longer than a day or two.
What's usually normal after the flu vaccine
The expected reactions are mild and short-lived:
- A tender, slightly red or swollen spot where the injection was given.
- A mild fever in the first 24–48 hours.
- A day of extra tiredness or being a little run-down.
- Mild muscle aches or a general 'off' feeling that passes quickly.
- Slightly reduced appetite or mild fussiness on the day, easing by the next.
- Your child otherwise drinking, playing and behaving much as usual.
How long flu vaccine side effects last
- Soreness or redness at the injection site: usually 1–2 days.
- Low-grade fever: typically settles within 1–2 days.
- Tiredness and mild aches: generally gone by the second day.
- Reduced appetite or fussiness: usually back to normal within a day.
Short and mild
Flu vaccine effects are brief. Symptoms that drag on for several days, or that get worse rather than better, are more likely a coincidental infection and worth a check.
Home care after the flu vaccine
Simple comfort measures are all that most children need:
Comfort & the injection site
- Gently move or use the arm or leg as normal — keeping it active helps ease soreness.
- A cool, clean, damp cloth held on the site for a few minutes can soothe tenderness.
- Offer extra cuddles and reassurance to a fussy baby or toddler.
- Avoid pressing, rubbing hard or putting anything on the injection spot.
Fever & fluids
- Offer plenty of fluids and dress your child in light, comfortable layers.
- If your child is uncomfortable with fever, you can give paracetamol in the dose your doctor has advised for your child's weight.
- Never give aspirin to a child — it is unsafe in children and especially risky around flu.
- Let your child rest and keep the day gentle if they seem tired.
Warning signs — see a doctor urgently
Serious reactions to the flu vaccine are rare, but seek urgent care for:
Seek urgent medical care if your child has
- Signs of a severe allergic reaction — difficulty breathing, wheezing, swelling of the face, lips or tongue, or widespread hives (usually within minutes to an hour of the shot).
- Sudden paleness, floppiness, or your child being very hard to wake.
- A high fever with your child looking seriously unwell, or a fever in a baby under 3 months.
- A febrile seizure — a fit or convulsion during a fever.
- Fast, laboured or noisy breathing, or your child struggling to catch their breath.
Call your doctor immediately — or go straight to the nearest emergency department.
🩺 Find a paediatricianFor trouble breathing, facial swelling or unresponsiveness, go straight to the nearest emergency department — don't wait.
When to call your paediatrician
Not an emergency, but worth a call:
- Fever that lasts beyond about 48 hours or keeps rising rather than settling.
- The injection site becomes increasingly red, hot, painful or swollen after a day or two.
- Your child seems genuinely unwell rather than just mildly off-colour.
- You have a child with egg allergy and want to plan how and where the vaccine is given.
- Any symptom that worries you or seems more than the mild effects described here.
Frequently asked questions
Can the flu vaccine give my child the flu?
No. The injected flu vaccine is inactivated — it contains no live virus and cannot cause flu. If your child gets a mild fever or aches for a day afterwards, that's the immune system building protection, not an infection. Catching flu around vaccination time is usually a coincidence, as it takes about two weeks for full protection to develop.
Why does my child need a flu shot every year?
Flu viruses change from season to season, and the protection from one dose fades over several months. A yearly vaccine is updated to match the strains expected that season and tops your child's protection back up, which is why it isn't a one-time shot.
My child is allergic to eggs — can they still have the flu vaccine?
In most cases, yes. Current guidance is that most children with egg allergy, including many with severe allergy, can be safely vaccinated. Tell your paediatrician about the allergy so they can advise on the right vaccine and the safest setting — it's a conversation to have, not usually a reason to skip the shot.
Can I give aspirin if my child has a fever after the flu shot?
No — never give aspirin to a child. It carries a serious risk in children, particularly around flu. If your child is uncomfortable with fever, use paracetamol in the dose your doctor has advised for their weight instead.
Is it worth vaccinating my baby against flu at all?
Yes. Flu can be much more serious in babies and young children than in adults, sometimes leading to breathing problems, ear infections or hospital admission. The vaccine's mild, short-lived effects are a small trade for meaningful protection during flu season.
My child had the first flu dose — why is a second one needed four weeks later?
A child being vaccinated against flu for the very first time needs two doses about four weeks apart to build full protection. From the following season onwards, a single yearly dose is enough.
Your next steps
Track your baby's vaccines
Enter your baby's birth date to get a personalised vaccine timeline with reminders, so no dose slips.
Open Vaccination TrackerVaccination schedule India
The full IAP-style immunisation chart from birth to the teen years, explained in plain language.
See the full scheduleFind a paediatrician
Worried about a reaction, or due for the next dose? Find a trusted paediatrician near you.
Find a pediatricianRelated vaccine guides
Sources
- WHO — Vaccine safety and side effects
- Indian Academy of Pediatrics (IAP) — Immunization guidelines
- CDC — Possible side effects from vaccines
- NHS — NHS vaccinations and when to have them
- WHO — Influenza (seasonal) vaccines
- CDC — Flu vaccine safety in children
- NHS — Children's flu vaccine
Next review due: 6 January 2027.
Continue on ParentVibes
Medical disclaimer
This page is educational information about common vaccine reactions and is not a substitute for medical advice, diagnosis or treatment. Every child is different — always follow the guidance of your paediatrician or vaccination centre. If your child has trouble breathing, swelling of the face or throat, a fast heartbeat, hives all over, dizziness or weakness soon after a vaccine, or seems seriously unwell at any point, seek emergency medical care immediately. When in doubt, always get your child checked — it is never a waste of anyone's time.
Read our Medical Disclaimer, Editorial Policy and Medical Review Policy.