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Thursday, November 21, 2002In a study of 2,392 young women, half of them vaccinated and half given placebo shots, the vaccine was 100 percent effective. Followed for 17 to 27 months, no vaccinated women developed infections or precancerous growths from the virus, whereas 41 nonvaccinated women did become infected, including 9 with precancerous cervical growths. The infection rate for unvaccinated women is admittedly low (41 out of 765), but that zero percent infection rate in the vaccinated is pretty hard to beat. The study focused on only one variant of human papilloma virus, HPV-16, which is has the highest association with cervical cancer of all its relatives, and it only looked at women because the focus of the vaccine is to prevent cervical cancer. HPV, however, is also a disease of men. It causes genital warts, and it can cause cancer of the rectum, anus, and penis, although these don’t occur with anywhere near the frequency of cervical cancer. It would be interesting to know, however, how the vaccine behaved in men. If it worked well in them, too, vaccinating both men and women could help eliminate HPV all together. Interestingly, the same issue of the NEJM, includes a study that tests the efficacy of a vaccine against genital herpes. It wasn’t nearly as successful. It decreased the incidence of herpes, but it didn’t completely eliminate it. And that reduction was seen only in women. For some reason, men had the same rates of herpes infections whether they were vaccinated or not. The researchers speculate that it might have something to do with the differences in the skin of the penis and the vagina. The penis has a tougher outerskin layer than the vagina, which is where most women get their infections. You would think that the better skin barrier in men would protect them more from the disease, but it turns out that the vagina compensates for its thin skin with secretions bathed in white blood cells and proteins that help confer immunity against infections. It’s only a theory, but it could be that the vaccine boosts that immunity against the herpes virus in women, whereas men don’t have that advantage. So, testing the HPV vaccine in men may be a worthwhile objective. The consequences of male HPV infection aren’t as devastating as the worldwide incidence of cervicial cancer is, but it does have implications for transmission of the virus, especially among same sex partners. posted by Sydney on 11/21/2002 08:35:00 AM 0 comments 0 Comments: |
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