Michael Shermer in Skepticblog:
Years ago you invited me to appear as a fellow skeptic several times on your ABC show Politically Incorrect, and I have ever since shared your skepticism on so many matters important to both of us: creationism and intelligent design, religious supernaturalism and New Age paranormal piffle, 9/11 “truthers”, Obama “birthers”, and all manner of conspiratorial codswallop. On these matters, and many others, you rightly deserved the Richard Dawkins Award from Richard’s foundation, which promotes reason and science.
However, I believe that when it comes to alternative medicine in general and vaccinations in particular you have fallen prey to the same cognitive biases and conspiratorial thinking that you have so astutely identified in others. In fact, the very principle of how vaccinations work is additional proof (as if we needed more) against the creationists that evolution happened and that natural selection is real: vaccinations work by tricking the body’s immune system into thinking that it has already had the disease for which the vaccination was given. Our immune system “adapts” to the invading pathogens and “evolves” to fight them, such that when it encounters a biologically similar pathogen (which itself may have evolved) it has in its armory the weapons needed to fight it. This is why many of us born in the 1950s and before may already have some immunity against the H1N1 flu because of its genetic similarity to earlier influenza viruses, and why many of those born after really should get vaccinated.
Vaccinations are not 100% effective, nor are they risk free. But the benefits far outweigh the risks, and when communities in the U.S. and the U.K. in recent years have foregone vaccinations in large numbers, herd immunity is lost and communicable diseases have come roaring back. This is yet another example of evolution at work, but in this case it is working against us.