I think of evolution as an error-making and error-correcting process, and we are constantly learning from experience.

Reply when questioned on the safety of the polio vaccine he developed: It is safe, and you can't get safer than safe.

As a child I was not interested in science. I was merely interested in things human, the human side of nature, if you like, and I continue to be interested in that. That's what motivates me.

What you see in living systems, and in genetic systems, is that the genes are already there, having arisen in the course of time, and when they are needed they become activated. If they had to be invented, the time would be too late.

There is no such thing as failure, there's just giving up too soon.

[Who owns the patent on this vaccine?] Well, the people, I would say. There is no patent. Could you patent the sun?

My ambition was to bring to bear on medicine a chemical approach. I did that by chemical manipulation of viruses and chemical ways of thinking in biomedical research.