Friday, February 8, 2008

Gardasil for Everyone!

When Gardasil, the vaccination against human papilloma virus (HPV), came on the market in late 2006, I figured it's about 30 years too late for me. HPV has been proven to cause cervical cancer (as well as genital warts). But Gardasil is approved only for girls and young women aged 9 to 26, on the assumption that they're less likely than older women to have already been exposed to all four strains of the virus covered by the shots.

So far, those of us over 26 don't have any way to prevent HPV infection and its potentially disastrous consequences (other than abstinence - not bloody likely!). Yet we're increasingly confronted with the knowledge of our HPV status, as testing for HPV gradually becomes routine. My ob/gyn offered it to me last spring, and my insurance covered it.

Luckily, the test showed I'm not currently infected with HPV. I'm pretty sure I had an active infection for several years in my twenties, when I kept getting moderately abnormal results on Pap smears. Most people eventually clear the virus spontaneously; I assume that's what I did.

One nasty feature of HPV, though, is that it can be reactivated, a trait it shares with a number of other particularly nasty viruses. Some of these just cause great misery - like the varicella zoster virus, which causes chicken pox in kids but shingles if it's reactivated later in life. But others, including Epstein-Barr (the mono virus), have been implicated in causing certain types of cancer.

I'm speculating a bit here, but it seems to me that reactivation is the most plausible explanation for at least some cases of cervical cancer in older women - those in their 50s or 60s and older who've been monogamous for decades, with a monogamous partner, and who probably weren't actively infected for all those decades.

But maybe it's not too late for me and my ilk, after all. A recent study by Merck, Gardasil's maker, found that it reduced the rate of HPV infection and pre-cancers in women aged 24 through 45. I'm wondering if the vaccine might help the body keep the virus in check at undetectable levels, even though Merck's press release on the study doesn't suggest this. To qualify for the study women had to be free of at least one of the flavors of HPV that Gardasil targets. But the vaccine's impact was so dramatic, it doesn't seem plausible to me that its only effect was to prevent fresh infections:
Also as a primary analysis, GARDASIL prevented 83 percent (95% CI: 51 to 96%) of persistent infection, low-grade cervical abnormalities and pre-cancers, and external genital lesions caused by HPV types 16 and 18 alone (23 cases in the placebo group and four cases in the vaccine group). In a secondary endpoint, GARDASIL prevented 100 percent of persistent infections, low-grade cervical abnormalities and pre-cancers, and external genital lesions caused by HPV types 6 and 11.
The press release doesn't say anything about the sexual habits of study participants - whether their sex lives were more like Samantha's in Sex and the City, or more like, well, mine. Obviously this information would help us understand whether Gardsasil mostly blocked new infections or mostly prevented reactivation of old ones.

This isn't just a theoretical question. It matters because if Gardasil hinders reactivation, then women of any age ought to consider getting the shots.

Gardasil might benefit men, as well. HPV has been pretty conclusively linked to oropharyngeal (mouth and throat) cancer, as well as cancer of the penis and anus. Having oral sex with six or more partners triples one's risk of oropharyngeal cancer. What's more, vaccinating men would contribute to herd immunity, thus reducing the risk to the entire population.

And no, I don't work for Merck. I realize this is a new vaccine and it might still turn out to have some untoward side effects. So far, though, its benefits seem to vastly outweigh its risks.

Unless, of course, you buy the wingnut idea that immunizing young girls will turn them all into sluts. Lynn Harris at Broadsheet has brilliantly put their objections into limerick form:
Why block a vaccine? Here's our answer.
Gardasil is no values-enhancer.
To prevent HPV
Causes sex, don't you see?
And quite frankly, we prefer cancer.

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