By Robert Bazell Chief science and health correspondent
NBC News
updated 5/12/2011 12:39:06 PM ET 2011-05-12T16:39:06

Starting treatment for HIV immediately after diagnosis is the most effective method yet discovered for preventing an infected partner from passing the virus that causes AIDS to a healthy partner, according to many experts.

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A U.S. National Institutes of Health sponsored international study of 1,763 mostly heterosexual couples released Thursday finds that the drugs used to treat AIDS can almost totally eliminate the transmission of the virus.

The study began in 2005 and was supposed to last 10 years. But the results were so dramatically positive that a committee that monitors the results halted the study five years early.

In all the couples, one partner was infected and the other was not. In half of the couples in the study, the infected partner got the drugs used to treat HIV infection immediately at the start of the study. In the other half, the infected partner got the drug at the normal medically indicated time — when his or her immune system began to deteriorate. At the time the study began, the HIV-infected partners had CD4 T-cell levels — a key measure of the immune system — of between 350 and 550 cells per cubic millimeter. A normal count is between 500 and 1,500.

In the 882 couples where the drugs were used in the normal way, 27 partners became infected with HIV. But in the 881 couples where treatment began early, only one was infected.

Previously, anecdotal reports have indicated that people who are being treated with the drugs are less likely to infect others. Scientists say it makes sense because the drugs reduce the amounts of virus in the body. But this is the first study to rigorously prove the concept.

During the study, both group were counseled on safe sex and given free condoms.

The study was carried out a several sites, mostly in African and Asian countries.

There were very few couples in the United States. Only a few gay male couples were in the study so officials say they can not draw any rigorous conclusions for that population. But many infected gay men in the U.S. and other countries, according to doctors, already, take the drugs to reduce the risk of infection. However, officials emphasize that this medical approach should never be used as an approach for safe sex practices.

The study also raises the issue of access to the drugs in poor countries. Already — for financial reasons — only a small percentage of people who need the drugs to save their lives get them. Expanding the use for the prevention of transmission raises the same issues of access to the drugs.

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Video: New hope for AIDS prevention

  1. Closed captioning of: New hope for AIDS prevention

    >>> we have a potential break through to announce in the strug dell to prevent the transmission of hiv . in a new study, they found a new combination of drugs which drastically reduced transmission in the virus. robert bazell is here with nbc news and joins us now. we're just ahead of the 30-year anniversary, as you were pointing up, on june the 5th.

    >> that was the discovery of this unusual disease and it's come a long way and now there are drugs that we have known since the late '90s are used to treat hiv , the virus that causes aids. the study shows that people who are treated heavily with the same drugs that are used to treat hiv are much less likely to infect their sex partners. it was a study of more than 1700 couples around the world financed by the u.s. national institute of health .

    >> so it's a really large study but they had such good results early on, they cut this clinical trial early.

    >> that's right. they started in 2005 and it was supposed to go on for ten years but the results were so good that they stopped it five years early. what they found -- and these are mostly heterosexual couples, where one person is infected and the other is not. they started the treatment right away, not when their immune system starts to decay. so in those people where they had early and constant treatment, there was only one case of transmission and the other half there was 27 cases of transmission when people got the drugs when they needed it as go downhill.

    >> what does this revelation mean to the general public ? how soon could people be seeing this and getting the medication?

    >> already it's been used where there's one infected pirn to try to cut down the risk of infection. it makes a lot of sense because these drugs are known to reduce the amount of virus in the body so therefore it would stop the transmission and it's very logical. but this is the first rigorous study to prove it. this was mostly -- in fact, all heterosexual couples. what it means for gay couples is not at all clear and also done mostly in african and asian countries where there is a shortage of drugs for the people. there is still this big question of access to the drugs. if there's not enough to give it for treatment, how can you give even more for prevention, even though you would prevent a lot of infections.

    >> weech reached so many strides. when do you think we will be sitting here with a cure?

    >> i have been sitting here for my entire career talking about this disease and it's been a horrible, vicious enemy. there's great progress for the people with who can afford it and have access to it, there's a treatment. but there has never been a single person cured and from those first six cases, the reported 30 years ago, there are now 75 million people in the world who have been infected with this virus.

    >> it's amazing to think that we're coming up on the 30-year anniversary. in the aids walk new york .

    >> good for you.

    >> it's great when we have news like this that we can pass on and it will be interesting to see how it develops with everybody getting access and more information to come as we learn more from this. bob, always great to see you.

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