One of the biggest problems with the vaccination question is the media and their policy of "balance".
Clearly if you have someone from the Labour Party arguing that we should have a financial growth policy, then it is right to balance the argument with someone from the Conservative Party arguing that we should have cuts. This is because either answer could be correct and it isn't clear cut.
Unfortunately, the media have got this idea of "balance" applied completely incorrectly when it comes to science. With the MMR vaccine, the absolute vast majority of medical scientists agreed that the vaccine was "safe", and this conclusion was supported by data (note, that "safe" does not mean that there are no risks, just that they are below a threshold deemed acceptable - there is still a chance that it could cause harm to a child in an extreme case, but this is very very low). However, a very small group of scientists contradicted this argument (this is completely fine and one of the great things about the scientific method - challenging each other makes sure it is science, not a belief system) and this was represented in the media (in a big way).
Where the media get it wrong is by giving equal weighting to both sides of the argument and making it seem like it is a 50/50 split in scientific opinion. This leads the unwashed masses to think that the challenge is strongly valid (which is wasn't). If the media gave a time slot (or number of words on the page) proportional to the quantity of scientists who support each side of the argument, then there would have been a 1 hour segment on how MMR is "safe" and about 1 second on how it causes autism.
Basically - the media are stupid and so are we all for listening to them. Don't forget, they are trying to SELL US NEWSPAPERS, and don't care for the welfare of our children, so ignore their opinion.
The problem is, that it is very difficult to put scary things into perspective. I know someone who refuses to travel on the underground because of the risk of a bomb attack. He also hates flying because of the fear of crashing. But if you take the number of people who use these two forms of transport every day, and the number of people killed from these (admittedly horrific) events, then your chances of coming to harm are infinitesimally tiny such that they can be called "safe" (just like a vaccine). But this argument is of no comfort to my friend and he is still scared! Interestingly, the same person make no fuss when jumping into the car to drive to the shops, which is nowhere near as "safe".
Clearly there are people who are at higher risks from vaccines and therefore they are not "safe" for them, but the medical professionals will give guidance in this situation - not the newspapers or your mate on mumsnet who is a quack.