Post-immunisation fever

What causes post-immunisation fever?

When your child has an immunisation, they are given a vaccine that causes their body to produce antibodies that help fight disease.

Vaccines often contain small amounts of weakened or dead viruses or bacteria. This stimulates your little one's body to produce antibodies without actually becoming infected with the disease. These antibodies will help them fight off the disease if they come into contact with the real, full strength virus or bacterium.

If they react to it, they can develop a slight fever. This is not unusual, and it shouldn’t last longer than a couple of days.

You might also notice a small lump that looks red and sore, where your child had their immunisation. This is common too, and should also go away without any special treatment.

If your child really feels out of sorts, then take them along to your GP for a check up.

How can I help my child feel better?

You can treat a fever caused by your baby’s immunisations in just the same way as you’d treat a fever caused by a cold or the flu.

• Make sure your little one gets plenty of restful sleep.
• Keep them cool –undress them to their underwear. You can cover them with a cool, light sheet though.
• Make sure they have plenty to drink. If they have started eating solid food, offer lots of cool drinks, especially water.

If your baby is still uncomfortable, you can treat a fever at home with a medicine containing infant paracetamol. CALPOL^® Infant Suspension is suitable for babies over 2 months, weighing over 4kg and not premature.

Or you can use ibuprofen. CALPROFEN^® Ibuprofen Suspension starts work on a fever in just 15 minutes and lasts up to 8 hours. It’s suitable for children over 3 months and weighing over 5kg.

For help deciding whether to choose paracetamol or ibuprofen, you should read our quick guide.

Read our guide on whether to choose paracetamol or ibuprofen

More about immunisations

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 to immunisations for you.

Read our introduction to your baby’s immunisations

We’ve also created a handy guide to your little one’s immunisations, which you can download. It shows you the different stages at which your child gets different vaccines, and explains how to take care of your little one after an immunisation.

Download our handy immunisation guide