Saturday, December 4, 2010

Not that there's anything wrong with that...

Remember Seinfeld? That was his mantra when discussing homosexuality. There was a whole episode, "The Outing" that featured the line over and over. Today I came across this article in the Washington Times on a new pill which can help lower the risk of a gay man contracting HIV from an HIV-positive partner. The numbers are interesting. the article states
Research subjects who took a pill called Truvada every day — plus used other AIDS-prevention strategies — lowered their risk of getting HIV by about 73 percent.
Men who failed to take the pill every day had only a 21 percent lower risk of getting HIV
It also was only effective with men who are confirmed as HIV-negative and who practiced additional prevention strategies such as consistently using condoms, getting treatment for other sexually transmitted diseases and reducing the number of sex partners.
Only 21% lowered risk? Compared to what? One would assume lower than not using the pill. But why then do they say that the effectiveness requires consistently using condoms, etc. Just what is the reduction in risk afforded by condoms?

I recall reading somewhere that condoms reduced the risk of contracting AIDS by 60%, but I didn't have a source. So I went googling. I visited literally dozens of sites that claims that condoms were "highly effective" but didn't give numbers and didn't quote a source that gave numbers. I finally found Worksop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention from the National Institutes of Health. The results are not promising.
In general, the Panel found the published epidemiology literature to be inadequate to definitively answer the question posed to the workshop participants. Most studies reviewed did not employ a prospective design, which is the optimal method to assess the effectiveness of condoms in preventing infection.
The "highly effective" numbers seem to come from a laboratory study of condoms, which was then assumed to apply to actual use. The first assumption was that since the FDA specifies that no more than 1/400 condoms fail a water leak test that 399/400 condoms will not leak in actual use. Then they assessed virus passage through a "perfect" condom using a liquid with a high concentration of virus. assuming that the chosen liquid behaved like semen and that a high concentration behaved like a low concentration of viral particles (which is a known false assumption - I can't find the paper, but at higher concentrations, multiple particles jam small holes and so they are less likely to pass through than at low concentrations).

That information was used to form a hypothetical risk model. The results appear to be nonsense. There are too many obvious things wrong with this model to go into here (I have to wonder who approved the "research"), but suffice it to say that if this model were true, then condoms would be nearly 99.399196% effective at preventing pregnancy (yes, that's the level of accuracy claimed by the model), and they are not. Real world studies show that about 16-20% of couples who use condoms regularly experience pregnancy within their first year of use (the paper uses the number 14%).

When a model doesn't predict real world data, the model is wrong.

There were several studies done on actual people for HIV, however. They considered only passing HIV between men and women during vaginal intercourse, not transmission among gay males, but one would hope the results were similar, or at least it's less of a stretch than the hypothetical model. The results look more realistic.
Overall, Davis and Weller estimated that condoms provided an 85% reduction in HIV/AIDS transmission risk when infection rates were compared in always versus never users.
This means that condoms are as effective against HIV as they are against pregnancy, which is still not very effective, considering the number of unintended pregnancies for condom users. A 1-in-6 chance of contracting a deadly disease for which there is no cure doesn't seem "highly effective" to me.

So condoms are not the answer they are claimed to be. Let's hope this new pill is not only effective as effective as claimed, and that it doesn't lead to more resistant strains of HIV if it is used as prophylaxis.

However, that's not what I intended to blog about. The thing that struck me most about the article was the rate of infection.
Men who have sex with men (MSM) represent "nearly half of all people living with HIV in the U.S., and the rate of new HIV diagnoses among MSM is more than 44 times that of other men," the CDC said.
We are living in a country that's considering regulating eating habits because overweight people have a 40% higher chance of contracting cardiovascular disease. Why don't we consider lifestyle choices that result in a 4300% higher chance of contracting HIV? We just repeat the mantra "not that there's anything wrong with that" and ignore the suffering of these people.


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