What Are The Potential Side Effects Of The MMR Vaccine?

Like all vaccines and medicines, the MMR vaccine cannot be declared completely 100 per cent safe. It is recommended that children with a severe egg allergy be carefully monitored after receiving the vaccine (it is prepared in the laboratory using hens eggs as a growth medium) and vaccination tends to be delayed in children who are ill with a fever at their appointment.

Some children do get side-effects to the MMR vaccine, especially after the first injection. Six to 10 days after the immunisation, some children may become feverish (this happens to about 1 in 10 children). Some develop a measles-like rash and go off their food. About one in every 1000 immunised children may have a fit caused by the fever, called a 'febrile convulsion'.

It is important to keep the risks in perspective, however. All of these effects and symptoms are very much worse if the child were to catch one of the illnesses. The worse side effect is that one in one million children develops encephalitis – swelling of the brain. However, one in only 200 children can develop encephalitis after getting measles.