All vaccines go through rigorous testing and regulatory processes that can take up to 15 years to ensure they are safe and effective. Like all medicines, vaccines can cause side effects, but not everyone gets them.
The frequency and type of side effects are slightly different for the two chickenpox vaccines used in the UK. For full information on side effects, ask for the patient information leaflet for the vaccine you are offered. As a general guide, the following side effects may be experienced:
Very common - affecting more than 1 in 10 people at each dose:
- reactions at the site of the injection, including redness, pain and swelling.
- raised temperature (fever)
Common - affecting up to 1 in 10 people at each dose
- chickenpox-like rash (in up to 10% of adults and 5% of children)
- mild cold-like symptoms
- irritability
- itching at the injection site
Uncommon - affecting up to 1 in 100 people at each dose:
- swollen glands, headache, sore throat, cough, or runny nose
- feeling sick or being sick
- diarrhoea
- a rash with blisters
- joint or muscle pain
- very high temperature
- drowsiness, tiredness, or feeling generally unwell
For rarer side effects - affecting fewer than 1 in 1000 people - please read the patient Information leaflets for Varivax and Varilrix.
For information about the MMRV vaccine in the UK, visit the MMRV Vaccine page.
As with any vaccine, medicine or food, there is a very small chance of a severe allergic reaction (anaphylaxis). Anaphylaxis is different from less severe allergic reactions because it causes life-threatening breathing and/or circulation problems. It is always extremely serious but can be treated with adrenaline. Health care workers who give vaccines know how to do this.
In the UK between 1997 and 2003 there was a total of 130 reports of anaphylaxis following ALL immunisations. Around 117 million doses of vaccines were given in the UK during this period. This means that the overall rate of anaphylaxis is around 1 in 900,000.
If you are concerned about any reactions that occur after vaccination, consult your doctor. In the UK you can report suspected vaccine side effects to the Medicines and Healthcare products Regulatory Agency (MHRA) through the Yellow Card Scheme. You can also contact the MHRA to ask for data on Yellow Card reports for individual vaccines. See more information on the Yellow Card scheme and monitoring of vaccine safety.