Megan McArdle (Asymmetrical Information) posts about HPV immunization — she thinks it's good even if it's mandatory (which the Texas version apparently isn't) — and draws, among others, this comment:

HPV, like HIV and unlike Polio, Tetanus, Pertussis, etc is 100% preventable by behavioral change.

Let me stress it again: It is 100% preventable (setting aside rape and congenital transmission) by behavioral change — lifelong sexual abstinence. It is not preventable by only having sex within marriage, since your husband or husbands (even the most religious don't mind remarriage after a spouse's death) might have been infected with HPV when you married them, or might cheat on you after marriage, get infected, and reinfect you.

Having fewer sexual partners will decrease your chances of getting infected, but they won't decrease them by 100%, and the chances will remain pretty substantial, I'd wager, given that "At least 50% of sexually active people will get HPV at some time in their lives." Having one sexual partner and making sure that he was a virgin at the time decreases the chances further (if he doesn't cheat on you), but, you know, sometimes the person you fall in love with — even the person you think God may have meant for you, if you think about things that way — happens to have done some wrong things in the past. If "behavioral change" means "dumping the one person you've fallen in love with and want to spend the rest of your life with because they've had sex with some other people" (or even "because they fall within the 50% of the public that has been infected with HPV"), then it might be good to make that clear (though again even that won't give you 100% immunity unless you are 100% confident that your spouse won't cheat on you).

And of course on top of all this, we know that teenagers, even well-brought-up teenagers, aren't always the best at behavioral change. However moral you might be, and however moral you are bringing up your daughter, are you 100% sure that she's going to take that supposed 100% prevention approach? If your religion teaches that sin, and giving in to temptation, is part of human nature — and if you think our society has turned into a moral cesspool that constantly bombards young people with praise of sexual immorality — then why do you think that even well-intentioned, well-taught teenagers are going to be able to completely resist temptation and sin?

Look, if we're talking assumption of risk and "you could have prevented it yourself" in the context of skydiving or bungee-jumping, I can understand that. But if "100% preventable" means living an entirely asexual life, and "almost 100% preventable" means dumping the person you're in love with because he isn't a virgin (and maybe is even part of the 50% of the public that's HPV-infected), then we're way out of the range of normal assumption-of-risk talk. And when you add to that the fact that failure to immunize turns the unimmunized into unwitting but still dangerous vehicles of transmission of deadly disease — when a woman dies of HPV-related cervical cancer, the unimmunized people who helped spread the HPV to the woman helped cause her death — then the case for "never mind immunizing, people should prevent HPV themselves because it's 100% preventable by behavioral change" becomes very weak indeed.