Studies show that about 2 out of every 3 babies get a fever over 38º C when they are given the MenB vaccine with other routine vaccines at 8 and 16 weeks of age. The level of fever depends on the child, and has nothing to do with how well the vaccine has worked. The NHS has produced a leaflet for parents on using paracetamol to prevent and treat fever after MenB vaccination .
Very common side effects in babies and children up to 10 years old (affecting more than 1 in 10 people at each dose):
- Fever between 38º C and 40º C (affecting about 2 out of every 3 babies)
- Loss of appetite
- Unusual crying
- Sickness and diarrhoea
Very common side effects in children, teenagers and adults (affecting more than 1 in 10 people at each dose):
- Pain, tenderness, redness, swelling, rash and/or hardness of the skin at the injection site
Uncommon side effects in babies and children up to 10 years old (affecting up to 1 in 100 people at each dose). You should consult your doctor if these occur, mainly to check that it is the vaccine causing these symptoms, and not some unrelated disease:
- High fever (over 40º C)
- Dry or itchy skin
Other possible side effects in children over 11 and adults:
- Painful muscles and joints
- Feeling sick
- Feeling generally unwell
More serious reactions to the vaccine have not been identified yet. However, there is not enough data to rule out the possibility of a rare but serious reaction.
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 were 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.
More information on side effects
Reactions listed under ‘possible side effects’ or ‘adverse events’ on vaccine product information sheets may not all be directly linked to the vaccine. See Vaccine side effects and adverse reactions for more information on why this is the case.
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.