Anybody want to try to make sense out of this? Or am I just missing something?

[William769]

Taking meds before exposure cuts HIV risk for heterosexuals

Heterosexuals who are HIV negative can significantly reduce their risk of infection by taking a daily dose of an antiviral drug, according to a new study by the Centers for Disease Control and Prevention.

The study, called TDF2, followed 1,200 uninfected heterosexual men and women between the ages of 18 and 39 years in Botswana, Africa. Study participants took a tablet containing tenofovir disoproxil fumarate and emitricitabine (TDF/FTC), whose brand name is Truvada, or a placebo. On average, patients were followed for a year although some were followed for about three and a half years. The risk of infection was reduced 63% overall, but for participants who actually got the drugs, that risk decreased by 78%.

Giving daily antiretroviral drugs to uninfected individuals to prevent the disease is called pre-exposure prophylaxis or PrEP. Previous studies have shown PrEP to be effective in reducing infection rates among the uninfected.

Dr. Kevin Fenton, director of the CDC's national Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, called the news a milestone. "It is clear we are not going to find one magic pill to solve the issue of HIV but by combining this approach with others we are beginning to get a better handle on combination packages. There is reason to be excited."

http://thechart.blogs.cnn.com/2011/07/13/taking-meds-before-exposure-cuts-hiv-risk-for-heterosexuals/?hpt=hp_t2

What about HIV - Gay people?

[Avalux]

1. The study was done in Botswana - study participants were heterosexual.

It would work the same way in homosexuals; HIV doesn't descriminate. Taking the drug as a prophylaxis will allow it to be in the bloodstream and block free virus from attaching to CD4 cells, thus cutting risk of infection. Same premise as giving anti-retrovirals to HIV pregnant women to keep the fetus/baby from becoming infected.

[TheWraith]

3. Precisely. I doubt that there'd be a statistically significant variation if you tested gay patients.

I'm just guessing here, but any change in the outcome would probably scale according to the overall risk of infection per sexual encounter, which varies by method. What that means is if (just making up numbers here to illustrate) the risk of infection from unprotected intercourse is 2% per instance, and the risk rate for unprotected anal sex is 3%, then you'd probably see half again more infectees among the gay male patients who practiced anal sex than among the straight patients studied.

That said, I think that this study seems kind of useless. Okay, one can bring down the risk of infection, but not eliminate it. How is that useful, when condoms do a more effective job at the same thing, and probably for far less cost than a retroviral pill? It's not reliable enough to, say, let a couple with one HIV+ partner dispense with safe sex.

This would be useful if it could be done as an after-the-fact treatment for accidental exposure, but it appears to require dosage beforehand. So... interesting scientifically, but practically useless.

[Avalux]

5. This is a way for heterosexual women in poor African countries to take control.

Condom use is not socially acceptable there; men will not use them and women will not suggest using them. It's a way to at least provide some protection to women who are very high risk of becoming infected.

Antiretrovirals do not kill HIV (no drug does); these drugs act as road blocks to the entry points HIV uses on the surface of CD4 cells to get into the cell and replicate. Taking the drugs prior to exposure provides protection (think of it as guards inside the fort waiting for the invasion); taking them after exposure would not be effective as the virus would already have a head start invading and infecting CD4 cells.

[TheWraith]

7. But is it practical?

Yes, it would cut down on infections if it were accessible to everyone, but how much to said drugs cost? And would the total cost per prevented infection of making them, distributing them, and teaching people to use them, be less than the cost per prevented infection of educating people about the importance of condom use?

[Avalux]

8. Educating about condom use is part of the strategy. It's slow going though.

The Gates Foundation provides funding for free drugs; other organizations do as well. Even a SMALL difference, saving a few lives so that children are not orphans, is worth it.

[yardwork]

10. The pharmaceutical companies created the drug because they think they can make money.

Will they make money on this in the developing world? Maybe not in Africa, but the pharmas are focused on China and India as huge emerging markets.

[just55650]

9. +100

[beyurslf]

2. The study is only pointing out the group that was targetted. It doesn't mean it wouldn't

work the same way for gay people. I doubt they would find many willing participants for a gay sex study in Botswana.

[fizzix137]

4. percentages sound funny

Participants who got one drug had 63% fewer infections over the placebo group. Participants who got the two drug mix had 78% fewer infections. Presumably good news for all at-risk groups.

[Avalux]

6. One drug......

blocks one of the receptor sites on a CD4 cell. The other drug blocks a different receptor site on a CD4 cell. If you take both, the infection rate goes down.