I had a big argument debate with a couple of friends on facebook about this.
I realised that although they'd done loads of research on the risks of vaccinations (some reasonable, but much of it from pretty dubious sources) they were woefully ignorant on the dangers of the actual diseases that the vaccinations were preventing.
They thought that Measles, Mumps and Rubella weren't that serious, and that they certainly couldn't kill you 
One of them didn't want to take a tetanus again as she thinks it gave her eczema the last time she took it. She had no idea that tetanus could be dangerous, she thought if she caught it, she'd just get treatment for it, wouldn't she? (My flatmate is a nurse and has been treating a patient with paralysis and brain damage after getting tetanus),.
They also had no knowledge of the risks of epidemics or pandemics.
I heard a very interesting podcast recently about the power of stories in assessing risks, and they related it to vaccination scares. It said that stories are a powerful way to get messages across, often more powerful than statistics.
They were saying that stories about vaccinations causing Autism etc stick in people's minds,. no matter what the evidence says, and that the health profession should try to counteract vaccination scare stories with their own stories, rather than rely solely on stats and evidence, as they don't fire the public imagination. I'll see if I can find the link ...
Story-telling rather than using evidence is a technique Cameron is using very effectively to manipulate the public at the moment, incidentally, but I digress 