"I can sort of understand, I don't agree with it but I can understand, how you can be sceptical about climate modelling. It's extremely complicated and abstract and the consequences are not fast," he said.
"In terms of vaccination, one of the great human achievements was the eradication of smallpox through a worldwide co-ordinated vaccination programme.
"It's probably one of the greatest achievements of modern civilisation. It killed hundreds of thousands, even millions of people throughout Europe and beyond, and it went - gone."
He said the anti-vaccination movement seemed to be about the freedom to choose what was best for your child.
"The psychology's relatively easy to understand, because I'm a parent. The idea that you will actively do something to your child which is slightly unpleasant for them, which is take them to the doctor and have a vaccination, is one of those things where you go, 'I'd rather not do that'.
"But it's clear that these childhood diseases that we've largely controlled or eradicated are going to begin rise back again if we, as a society, don't properly vaccinate our children.
"It's a huge risk."