Question: what is an MMR?

Richard Badge answered on 18 Jun 2011:

MMR stands for Measles Mumps and Rubella – it is a vaccine that makes people receiving it immune to these diseases. They are all quite common “childhood diseases” – which means that many children get them, and the vast majority get sick for a little but then recover (and are immune thereafter). Still some children do have complications that can be fatal, and as the diseases are common this can add up to a lot of deaths that can be prevented. Theses diseases can also be much more serious for adults – rubella is very bad for pregnant women and their unborn babies and mumps can make men unable to have children.

So what is needed is a way to make people immune without first having to have the disease. This is what vaccines do and they are very good at it, but they only work best if everybody is vaccinated, and can even lead to the disease being wiped out. For example polio was a childhood disease that caused paralysis in 10s of thousands of children and adults (sometimes paralysing their breathing muscles, which was fatal unless you were put in a machine that helped you breath).

Now vaccination has been so effective that the polio virus is very rare outside of high security laboratories where it is used for research and hardly ever causes disease anymore. Scientists are debating whether it should be completely destroyed. The argument for keeping it is that we can’t ever be absolutely sure it is wiped out in the wild (some viruses can hide in animals, without causing disease). So its probably a good idea to keep some so that it can be used to help make a new vaccine if a new type of polio evolves in the future.