When is MMR (mumps, measles and rubella) vaccine given?

The MMR vaccine cannot be given under 15 months because it is ineffective due to infants’ inherited immunity. Later, MMR is said to give lifetime protection to 90 per cent of recipients. The booster at four years is to catch the 10 per cent whose immune systems failed to create antibodies with the first exposure at 15 months. Children immunised against measles have a medically known one in one million chances of developing encephalitis from the immunisation — hence the vaccine must not be given to children with compromised immune systems as a result of rare immune disorders or chemotherapy. Mumps is one of the most common causes of viral meningitis (brain membrane inflammation) and viral encephalitis (brain tissue inflammation) in unimmunised children under 15 months of age. Between 1970 and 1991 there were epidemics of mumps every 3–4 years in New Zealand, with over 2000 hospital admissions. Since the MMR vaccine was introduced in 1992 there have been no further epidemics.

Rubella immunisations used to be given to 11-year-old girls, but this failed to stop the disease circulating. Now it is included with measles and mumps and given to both sexes — to protect females during future pregnancies, and to protect females from male carriers.