Greatest medical breakthrough since 1840?

So asks the British Medical Journal in this webpage, and many have responded with posts offering an array of answers. Check it out as it's being constantly updated.

My vote? Penicillin, which was discovered accidentally by Dr. Fleming and kicked off the era of antibiotics, which made possible the taming (of course not the end) of infectious disease, which had been the most common killer of people for thousands of years. (It still is the most common killer of people in most developing nations.)