A Daily Pill Can Prevent HIV Transmission, Two Studies Show

By Valerie Ross | July 15, 2011 11:15 am

What’s the News: A daily dose of anti-HIV drugs can significantly reduce the likelihood that straight men and women will contract HIV from an infected partner, according to two new clinical studies. These studies add strong evidence to earlier findings that taking HIV drugs can prevent healthy people from contracting the disease, and are the first to show that the drugs reliably lower transmission risk in heterosexuals.

How the Heck:

  • One study enrolled 4,758 straight couples in Kenya and Uganda, in which one partner—either male or female—had HIV and the other didn’t.
  • The uninfected partners were split into three even groups. Each group was given a different type of pill, which they were instructed to take daily: a pill containing the antiretroviral drug tenofovir; a pill with both tenofovir and another HIV drug, emtricitabine; or a placebo.
  • Over course of the three-year study, 47 participants taking the placebo contracted HIV, compared with 18 taking tenofovir and 13 taking the combination pill—meaning that the drug regimens reduced HIV transmission by 62% and 73%, respectively.
  • The other study enrolled over 1200 heterosexual men and women. Half the participants were given the tenofovir and emtricitabine pill to take daily, and the other half were given a placebo.
  • Overall, the risk of contracting HIV for people taking the drug was 63% lower than those for people taking the placebo pill. The researchers also looked just at participants consistently taking the drug—leaving out participants who had left the study or stopped taking the drug for at least a month—and compared them to the placebo group. Risk for this group, the team found, was reduced by 78% compared to the placebo group.
  • The results of both trials were so promising they were halted early; the drug was working so well the researchers could no longer in good conscience keep giving people the placebo instead.

What’s the Context:

  • A study last year of gay men in San Francisco showed the same effect: Taking tenofovir reduced a healthy participant’s risk of contracting HIV by 44% compared to men taking a placebo. For those who adhered most faithfully to the drug regimen, taking the pill almost every day, their risk dropped by 73%.
  • This April, however, a study testing this approach in African women was stopped early because the drug didn’t seem to be effectively protecting the women. Some researchers wondered if some women in the study were giving some pills to their infected partners—since these same pills are used to keep HIV infections in check—rather than taking them all themselves.
  • Worldwide, heterosexuals in Africa are hit hardest by HIV, says Kevin Fenton, director of AIDS prevention at the CDC, “and these studies offer the first compelling evidence that PReP can work to reduce HIV infection among them,” Time’s Healthland blog reports.
  • Preventative drugs alone won’t halt the spread of HIV, but experts are hopeful that they can make a big difference. “We’re beginning to understand that these antiretroviral drugs are powerful tools for prevention tool kits,” Fenton told the Wall Street Journal. Talking to the Los Angeles Times, Mitchell Warren, head of the AIDS Vaccine Advocacy Coalition, called the studies “two more nails in the coffin of HIV.”
  • These drugs are relatively cheap, an important factor in considering their use for widespread prevention. Gilead, the company that makes the drugs, sells them for as little as 21¢ per day in parts of the developing world.

The Future Holds:

  • The CDC has announced it will immediately start working with public health groups to formulate guidelines for using the drugs preventatively for heterosexuals in the US (interim guidelines already exist for gay men).
CATEGORIZED UNDER: Health & Medicine
  • debra cole

    i’m not young enough to be promiscuous and I’ve never been gay but just in case I need to help in a bloody mess of the highway sign me up
    Seriously, having watched people dying with aids a number of years ago i say if we can prevent one such horror lets meet in the streets and turn cartwheels
    thanks science

  • lyllyth

    How the hell did giving out a placebo pass the ethics committee for this study???

  • http://c2comics.com L

    lyllyth, you’re not actually a scientist, are you?

    Experimental drugs can cause more problems than the original disease – by the time it gets to human testing it’s unlikely but it is possible. Furthermore not using a placebo would not allow scientists to make an accurate correlation. If they all received the drug and HIV transmission was 90% less than those not taking the drug… well…who? Are you just picking up random people for the “non-drug” control? Why aren’t they getting the drug?

    Furthermore, if you tell people they are taking a drug that might reduce HIV transmission, and that’s it, some may engage in riskier behavior. “Oh, we don’t need to use a condom, honey, I’m taking that pill!” Not all people will do this, but some people do consider test drugs actual proven cures. If people on that pill engage in riskier behavior it may skew the results. If you tell people, however, “you might be on this drug, but you might be on this placebo that does nothing” the chances of them increasing their risky behavior is decreased.

    Finally, it is not as though these scientists injected HIV into test subjects. These subjects engaged in their normal activity. There are a number of ways to prevent HIV transmission from partner to partner. It’s not like the Tuskegee experiment.

  • http://c2comics.com L

    ps – I didn’t mean to insult you with the “you’re not a scientist” reamark, lyllyth, I just wanted to make sure anyone who’s reading this knows that this would be not only acceptable but necessary under ethical guidelines testings for potential treatments. Cancer trial patients get placebos all the time when new drugs come out. It *has* to be done this way for there to be any actual, logical conclusion drawn from the subsequent data.

  • AtomR

    It’s not the placebo part that shocks me to be honest. I know placebos are given in clinical trials to establish the effectiveness of taking the drug versus not taking the drug but am I the only one shocked that they actually, willingly incentivated uninfected people to have unprotected sex with hiv positive people. THAT is the ethical dilemma here.
    It’s one thing to give a cancer patient a placebo (they already have the disease) , its another to tell people they are being given an untested drug (placebo or not) that reduces chances of hiv-infection thus giving them a false sense of protection.
    I know these were couples and not stranges off the street but I still can’t see someone risking the health of their loved ones unless they were somehow missinformed about exactly how effective the drug was.

  • http://c2comics.com L

    “they actually, willingly incentivated uninfected people to have unprotected sex with hiv positive people. THAT is the ethical dilemma here.”

    Where in the world do you see that?

    HIV would not be the pandemic it is if
    1. Sexual transmission could be spread simply by using protection during sex
    2. People always used protection during sex.

    Number one? Is true. Unfortunately number 2 is not. I highly doubt ANYone told people to have unprotected sex and, again, as I said to lyllyth, one of the reasons for the placebo is to make sure people WOULDN’T increase the likelihood of having unprotected sex. I am 99% positive that the researchers simply said, “Here is a pill. It might be the placebo, so don’t change your sexual habits” and the people simply carried about as they had been, sometimes forgetting/neglecting to use condoms, sometimes experiencing condom failure, etc.

  • http://c2comics.com L

    Note also, this was done in Kenya and Uganda, where getting people to use condoms is already incredibly difficult (honoring a wife’s request to wear a condom could be considered a gift to her, not a responsibility). People are still being told condoms don’t stop HIV spread. I had a teacher who told me this – “a condom is just that – it’s a con and it’s dumb.” If a husband and wife are having sex, there is no need for a condom, she told us. This was in the mid-nineties, too, when HIV was really big. Thankfully I was able to see that teacher as an idiot, but not everyone is as fortunate.

  • http://c2comics.com L

    Oops, in above comment, meant “1. Sexual transmission could be prevented simply by using protection during sex”

  • Matt B.

    “Preventive”, not “preventative”. A useful rule (based on how the words were invented) is to take the “-ion” word, and just change the “-on” to “-ve”. It works with everything except “adaptation”.

  • http://c2comics.com L

    …there’s a pill that can prevent HIV transmission and you’re hung up on *grammar*?!


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