Post-immunisation fever in Children

It’s common for some children to develop a fever after an immunisation. If your little one feels unwell after an injection, you’ll want to do all you can to make them feel better.

From simple tips to help them feel more comfortable to doing all you can to bring down their fever, there’s lots of ways you can help.

Will my child have a high temperature or other side effects after vaccination?

Usually, any side effects will occur where the injection was given, including:

  • Swelling
  • Redness
  • A small hard lump

Though it may be sore to touch, these symptoms will pass in 2-3 days and you
don't have to worry about them.

Fever is also quite common in young children, but is usually mild.

What about febrile seizures (fits)?

Most febrile seizures occur when a child has fever caused by a common
infection (like flu, chickenpox or tonsillitis), but in very rare cases they can
occur after a child has a vaccination. Although febrile seizures can be frightening, they aren't usually a cause for concern. In very rare cases, a seizure can be a sign of a more serious condition, such as meningitis, which requires emergency medical treatment.


Dial 999 immediately to request an ambulance if your child:

  • is having a seizure that's lasting longer than five minutes and showing no signs of stopping

  • has a blotchy red rash that doesn't fade or change colour when a glass is placed against it (in some cases a rash isn't always present)

  • is having breathing difficulties

How do I know if my child has a high temperature?

Fever in children is usually defi ned as a temperature of over 37.5°C.
You should contact your GP, health visitor or practice nurse if your child is:

  • Under 3 months old and has a temperature of 38°C (101°F) or higher
  • 3 to 6 months old and has a temperature of 39°C (102°F) or higher
  • Any age, and, as well as fever, has other signs of being unwell such as floppiness and drowsiness

Find out how to take a temperature here.

How can I help them feel better?

  • Give your child plenty of fluids

  • Cover them with a lightweight sheet if necessary

  • Keep the room well aired and at a comfortable temperature (about 18°C or 65°F) by adjusting the radiators or opening a window.

  • If your child is distressed and uncomfortable, give them paracetamol or ibuprofen (paracetamol can be used from 2 months of age (weighing over 4kg and not premature) and ibuprofen from 3 months (weighing over 5kg)). This helps bring their temperature down. Always read the label to find out correct dose and frequency for your child's age.

Specific advice for the Men B vaccine

The Men B vaccine is usually given at your baby’s first and third immunisation
appointments at 2 months and 4 months of age, and a booster at 12 months.


Fever is particularly common with Men B vaccine at 2 and 4

Although fever can be expected after any vaccination, it is very common when
the Men B vaccine is given with the other routine vaccines at two and four
months. The fever tends to peak around six hours after vaccination and is
nearly always gone completely within two days.

The fever shows your baby’s body is responding to the vaccine (but don’t
worry - not getting a fever doesn’t mean it hasn’t worked). The level of fever
depends on the individual child and does not indicate how well the vaccine has

How can I reduce the risk of fever?
Giving paracetamol soon after vaccination – and not waiting for a fever to
develop – will reduce the risk of your child having a fever. This will also reduce
the chance of your baby being irritable or suffering discomfort (such as pain at
the site of the injection).


When your baby recieves the Meningitis B vaccine you should be asked if you have a supply of liquid infant paracetamol at home. If you do not, you may be offered a sachet and a syringe. You should then get some liquid infant paracetamol from your local pharmacy or supermarket on your way home. This is because post-immunisation fever is more common when the Meningitis B vaccine is given with the other routine vaccinations at 2 and 4 months.

You should give the first dose as soon as possible after your two-month
vaccination visit. You should then give the second dose 4-6 hours later and the
third dose 4-6 hours after that. You will need to follow the same steps after
your four-month vaccinations.


Current advice states that paracetamol should be used to treat postimmunisation fever in babies after their Men B injections at 2 and 4 months; in this instance, ibuprofen is not currently recommended. Your nurse will give you more information about paracetamol at your vaccination appointment and you may be given a leafl et to take away with you with written instructions.

When to call the doctor

Your child’s fever and any redness or soreness where they’ve had the injection should clear up within a couple of days.

If you’re concerned that your child is feeling very out of sorts and their symptoms are not getting better then take them along to your GP for a check up.

A bit more about immunisation

We know that your child’s immunisations are a really important part of their healthcare during their first few months and years, and that you’ll have a lot of questions about them. So our experts have written a simple introduction including the full UK immunisation schedule.

Read our introduction to your baby’s immunisations


See also

Dr. Carol Cooper on caring for a child with a fever
Dr. Carol Cooper on caring for a child with a fever

Watch our short video to find out how best to take care of your baby if they have a fever.

Watch our expert tips video

CALPROFEN® Ibuprofen Suspension
CALPOL® Infant Suspension


Contains paracetamol.
From 2 months, weighing over 4kg and not premature.

Full product details

Fever (high temperature)
Fever (high temperature)

When your child suffers from a fever, it can be a sign that their body is fighting off an infection. Make sure you know what to look out for and when a high temperature becomes serious.

More about fever

Contact the NHS

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