After having the vaccine there may be side effects, but these are usually mild.
Vaccines protect babies against the risk of very serious infections and should not be delayed.
After the MenB vaccine, side effects may include:
- redness, swelling or tenderness where they had the injection (this will slowly disappear on its own within a few days)
- being a bit irritable and feeding poorly
- a temperature (fever)
Fever (a temperature over 37.5°C) shows that a baby’s body's responding to the vaccine – although not getting a fever doesn’t mean it hasn’t worked. The level of fever will depend on the individual child and doesn't indicate how well the vaccine will protect the baby.
Fever can be expected after any immunisation, but is more common when the MenB vaccine is given with the other routine vaccines at 8 and 16 weeks.
Giving paracetamol will reduce the risk of fever, irritability and discomfort for your baby after immunisation (such as pain at the site of the injection). Ask your pharmacist for infant paracetamol for the MenB vaccine before the baby’s immunisations are due. Please bring the baby’s ‘red book’.
It's important that a total of 3 doses of infant paracetamol are given to babies when they receive both their first (8 week) and second (16 week) vaccinations.
To reduce the chances of fever you should give the baby:
- the first dose of infant paracetamol just before or just after the routine immunisation
- the second dose of infant paracetamol 4-6 hours after the first dose
- the third dose of infant paracetamol another 4-6 hours after the second dose
Fever is much less common when the MenB booster is given between 12 and 13 months of age so paracetamol isn't always needed then. However, if the baby does develop a fever, is irritable, or unwell, then you can give them infant paracetamol if you wish.
Information about treating a fever in children
In infants who do develop a fever after vaccination, the fever tends to peak around 6 hours after vaccination and is nearly always gone completely within 2 days.