Immunisation and childhood vaccination
Immunisation is the only effective preventive measure against acquiring measles.
The live attenuated measles vaccine induces an immune response that is similar to naturally acquired immunity and can be boosted by challenge from wild or vaccine virus.
Measles vaccine is at least 95% effective and seroconversion rates are close 100%. Primary vaccine failure of the first dose at 12 months of age or older occurs in up to 5% of people, but 95% of first dose failures will seroconvert from a second dose.
Maternal antibodies are the most common cause of primary vaccine failure. The age of first immunisation with measles vaccine must balance the chance of seroconversion with the risk of infection. This is why, in countries with endemic measles, the first dose of measles containing vaccine (MCV) is given as early as nine months, often complemented by another dose during the second year of life.
Experience and modelling shows that two doses of measles vaccine is required to interrupt indigenous transmission and achieve herd immunity. A single dose in the second year of life will induce immunity in about 95% of immunised people. This means that 100% uptake would be required in order to achieve the desired 95% immunity level. However, about 95% of those who fail to respond to a first dose develop immunity from a second dose and hence the benefit of a second dose.
All European immunisation programmes today promote a two-dose measles immunisation schedule with the first dose given during the second year of life and the second dose at an older age that differs between countries.
Measles vaccine is most commonly administered as part of a combination of live attenuated vaccines that includes measles, mumps, rubella or measles, mumps, rubella and varicella (MMR or MMRV).
Combination vaccines have been shown to elicit the same immune response as individual vaccines. Vaccinating individuals who are already immune to one or more of the antigens in the combination vaccine, either from previous immunisation or natural infection, are not associated with any increased risk of adverse events.
Regarding post-exposure prophylaxis, administration of an MCV is the intervention of choice within 72 hours of exposure as the incubation period for vaccine virus is shorter than that for wild virus.
The immunisation schedule for measles containing vaccines (MMR or MMRV) in the European countries can be found on the website of the European Community Network for Vaccine Preventable Infectious Diseases (EUVAC).
