Brian, your points are well taken about vaccinations. I should also have realized that whatever info I'd read about the girls-only study came from something I'd found here! In fact every chance I get I tell friends with young boys to get them vaccinated for HPV along with the girls, and some have done so.

And I couldn't agree more about the absurd, fear-driven anti-vaccine movement in the U.S. Ben Goldacre's book Bad Science, with which some here might be familiar, is an excellent read for a thoughtful and educated opinion about that issue and other medical quackery.