Baby vaccinations: what are the side effects?

It can be really tough going through this with your baby. So, well done. And I don't mean to sound patronising: I mean it. As a mum myself, I know it isn’t fun but, as a doctor, I also know it is the best thing to do
Dr Philippa Kaye, expert family GP and mum of 3

Once your child has had a jab, you may find they have some after-effects which can last for a few days. (You can read how to deal with each of them further on in this article.) They may include:

fever
loss of appetite
grizzliness
abnormal crying
soreness/swelling around where they've had the injection
vomiting/diarrhoea

Not every baby will have these side effects but they aren't uncommon. They are generally due to the vaccine stimulating your baby's immune system, so that it can recognise that particular bacteria or virus in the future and therefore protect them against the disease later on.

But whether or not your baby has any side effects does not mean the immunisations aren't working. Side effects or not, the immunisations will be doing their job!

Coping with your feelings

You're doing the right thing!

It's not nice to give your baby something which you know will make them cry and then may make them miserable for a day or so, but you are protecting them from potentially fatal diseases.

Vaccines work. They can save your child's life.

What are the key side effects after baby jabs – and how should I treat them?

I've listed the key side affects and how you should treat them below. But, first and foremost, whatever side effects your baby is experiencing, if they are also not keeping down any fluids or becoming floppy or unresponsive, seek urgent medical advice.

1. Fever

Fever (a high temperature, over 37.5°C) is probably the most common side effect of vaccinations. For all of us, fever is a common and general response to an infection and while having injections doesn't infect your baby, when injections are given, the body's immune system is stimulated in the same way – to try and provoke immunity – and so a fever may develop.

The Men B vaccines, in particular, have a high chance of having fever as a side effect. Because of this, it is recommended that you give your baby an age-appropriate dose of infant paracetamol after both doses of this vaccine (at 8 weeks and 16 weeks). Studies show that giving paracetamol after the meningitis B vaccine reduces the risk of developing a fever by about half. The nurse giving your baby their vaccine will generally give you information about this.

Fever is also more common after the 2nd and 3rd dose of the 6 in 1 vaccine (at 12 weeks and 16 weeks).

If you baby does develop a fever after their jabs, keeping them cool – so make sure they don't have too many layers of clothes/blankets – and give them plenty of fluids (breastfed babies may need extra feeds). If needed, you can use an age-appropriate dose of infant paracetamol.

As always, if you are concerned, please seek medical advice.

2. Loss of appetite

This can sometimes come when you have a fever, so don't be too surprised if your baby goes off their food for a while.

However, you do need to be careful that your baby doesn't get dehydrated. Signs of dehydration include:

a sunken 'soft spot' on the head
a few or no tears when they cry
a dry mouth
fewer wet nappies
drowsiness
fast breathing.

If you notice any of these symptoms, do see your doctor.

3. Grizzliness or more crying than usual

You might just find that, after their injections, your baby's just not their usual happy self – even if they don't get a temperature. They also may not sleep well.

There's no specific treatment for this, apart from checking for fever and checking that they are drinking. But I recommend lots of cuddles and reassurance!

4. Soreness/swelling around where they've had the injection

Local reactions, such as redness, swelling or pain/discomfort, around the injection site are common.

If your baby is showing distress and seems to be in pain because of any swelling around where the injection was (usually arms or legs), you can give them an age-appropriate dose of paracetamol-based medicine to ease their discomfort. And don't panic: this is a common side effect of an injection.

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If the swelling gets worse or isn't going away, then do see your GP.

6. Vomiting/diarrhoea

If you find your baby is being sick or has more dirty nappies than usual after their injections, it could well be connected with their jabs.

In particular, the rotavirus vaccination can lead to mild diarrhoea. Ensure that your baby has enough fluids, so offer more milk.

Do see a doctor though if you're at all worried or the vomiting/diarrhoea symptoms seem to be getting worse, or if there are any signs your baby might be dehydrated (see the signs above in the section about Loss of appetite.)

What about the MMR and 'mini measles'?

The MMR vaccine (at 1 year and 3 years) can have some specific side effects, namely 'mini measles' - which can occur 6 to 10 days after the vaccine, causing a fever, appetite loss and a measles-like rash.

You child may also get 'mini mumps' 14 to 21 days after the vaccination - causing fever and swollen glands.

If your child gets either of these, they are not infectious. And they should recover quickly.

About our expert Dr Philippa Kaye

Dr Philippa Kaye works as a GP in both NHS and private practice. She attended Downing College, Cambridge, then took medical studies at Guy’s, King’s and St Thomas’s medical schools in London, training in paediatrics, gynaecology, care of the elderly, acute medicine, psychiatry and general practice. Dr Philippa has also written a number of books, including ones on child health, diabetes in childhood and adolescence. She is a mum of 3.

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