What to Expect
After Your Child’s Flu Vaccine

(Advice for parents)

Possible Side Effects: What’s Normal, What’s Not

Common, mild side effects
These usually appear soon after vaccination and resolve within 1–2 days:

  • Muscle aches
  • Tiredness
  • Irritability
  • Reduced appetite
  • Headache
  • Runny or stuffy nose
  • Pain, redness or swelling at the injection site (if vaccinated by needle)
  • Some children may get a mild fever (high temperature)

Important note: These effects are generally mild and short-lived. They may feel a bit like mild flu symptoms, but the vaccine cannot give your child the flu.

Rare but serious side effects

  • Severe allergic reactions are very uncommon.
  • In very rare cases, Guillain-Barré syndrome (a nerve condition) has been reported. However, the risk of getting Guillain-Barré is higher if your child actually catches the flu than from the vaccine. 

If your child shows signs of a serious reaction (for example, difficulty breathing, swelling of the face or throat, hives, or sudden severe weakness), seek medical help immediately.

After the Vaccine: What You Can Do

  • Keep an eye on your child for mild symptoms (aches, tiredness, low fever) — these are expected and should fade in a day or two.
  • Encourage fluids, rest, and comfort measures (paracetamol or ibuprofen, as recommended by your child’s GP or pharmacist) to ease discomfort.
  • Monitor for any unusual or severe symptoms (see “When to Seek Medical Help,” below).
  • Continue general flu prevention strategies:
    • Frequent handwashing
    • Covering coughs and sneezes with tissues or the elbow
    • Disposing of tissues promptly and washing hands afterward 

When to Contact a Doctor

Contact your GP or seek medical help if your child:

  • Develops high or persistent fever (especially beyond 48 hours)
  • Becomes unusually drowsy, confused, or irritable
  • Has difficulty breathing, wheezing, or chest pain
  • Shows signs of a severe allergic reaction (swelling of face/lips, rash, difficulty swallowing)
  • Develops sudden weakness or numbness in limbs (rare)

Also, if you notice a side effect that concerns you or seems serious, you can report it via your local health authority or regulatory body (in Ireland, the Health Products Regulatory Authority, HPRA). 

Notes on household contacts who are immunocompromised

  • As a precaution, please keep your child away from household contacts who are immunocompromised – for about 2 weeks.