AIDS Vaccine Study Results Explained

A new AIDS vaccine tested on more than 16,000 volunteers in Thailand has protected a significant minority against infection, the first time any vaccine against the disease has even partly succeeded in a clinical trial. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, discusses the results.

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ROBERT SIEGEL, host:

Well, joining us now from Bethesda, Maryland, is Dr. Anthony Fauci, who's director of the National Institute of Allergy and Infectious Diseases. Welcome to the program once again, Dr. Fauci.

Dr. ANTHONY FAUCI (Director, National Institute of Allergy and Infectious Diseases): Good to be here.

SIEGEL: We've heard this described as a small success at last. It's a little less than half full, a steppingstone. How would you rate this achievement?

Dr. FAUCI: I would rate it just like that. It's very important, as you mentioned on the program, that this is the first time that we've ever seen what we call a positive signal for any HIV/AIDS vaccine in a human study. And we've been working on this for over two decades.

The effect, however, is only modest. So, this is not what we call a prime time or the endgame vaccine, certainly not. But it opens up a door to try and explore what the exact mechanisms of this protection is. And once you can identify what we call a correlate of immunity, what is it that we induced in these people that made a modest percentage of them get protected?

Once you identify that, then you can try and work on amplifying that and optimizing that so that you can in future vaccines do much, much better because nobody wants to settle for something that's only a modest effect. You want to do much, much better than this. So it is, as mentioned, a steppingstone.

SIEGEL: Yeah, it would seem that the vaccine itself, if it can reduce the risk of infection by only a third, that sounds - well, perhaps scientifically impressive, almost dangerous that it could engender a false confidence about its effectiveness.

Dr. FAUCI: Well, when you have prevention with HIV, for sure, you have to have multifaceted prevention modalities. You have to have behavioral change, condom distribution, treatment of injection-drug users, in certain countries, circumcision, etc.

SIEGEL: Mm-hmm.

Dr. FAUCI: I don't think regardless of what kind of a vaccine we get, even if we get a very effective one, you always have to implement other preventive measures. I don't think that there ever will be, or should be, a free-standing vaccine that, that's the only modality of prevention that you do.

SIEGEL: I'd like to pursue that a bit more with you because I'd like you to talk a bit about, frankly, the ethics of testing an HIV vaccine. If all the people in a test sample, in this case in Thailand, had practiced safe sex or avoided other risky behaviors, then the infection rates probably would have been much lower in both groups. Is it ethical to conduct a test that only has value if people expose themselves to a virus that they might be able to avoid exposure to?

Dr. FAUCI: That's an excellent question. And here's what we do in vaccine trials like this. Everyone, the people who get the vaccine and the people who get the placebo - are intensively instructed of what they need to do to avoid infection: what condoms do, how to use a condom, behavioral type of modification. So they get intensive counseling about how to avoid infection.

Unfortunately, human nature, being what it is, that people slip and they don't do that. And that's what happens, and that's why some people get infected. So, in fact, it makes the vaccine trial even more difficult. But ethically, you must do that. Counseling is a very, very important part of the vaccine trial.

SIEGEL: But the same researcher who counsels is actually hoping to have a useful study that people won't be safe.

Dr. FAUCI: That's not the case. As a matter of fact, you have nurse practitioners, people who are not the ones that are administrating the vaccines, there are special counselors who are dissociated from the scientist, who really want this to work.

SIEGEL: Is the test that we've heard about today, is this alone out there in the field, or there are a dozen other initiatives that might be creeping up on the same result? How far advanced are we toward an AIDS vaccine?

Dr. FAUCI: This is a trial that was what we call an efficacy trial involving a large number of people. In order to show if something is effective, you have to have large numbers of people because of relatively low infection rates. This is the only, what we call efficacy trial that's out there. There's a lot of experimenting going on now in animal models and small numbers of people, what we call proof of concept trials, where the trial is not large enough to tell you if something is going to work or not work, but it's going to give you some scientific information. Are you inducing the kind of response that you hope would be protective if it were used in a larger trial?

But the answer to your question is, there are no other large trials going on right now for efficacy. But this is going to take some years to get to that point. This is a process that's not going to be next year or the year after. It's going to be a gradual building block over several years.

SIEGEL: And was the trial in Thailand actually big enough, was the sample big enough, so that one could assume that everybody faced roughly similar risks of exposure to the virus?

Dr. FAUCI: Exactly. That's a very good question. It was randomized trial, so it's really matched for everything: for sex, for behavior, for age. All of those things are - when you randomize someone, you take them randomly and put them in one limb versus the other. And at the end of the time, those groups are really quite equal. It's a very important part of the statistics of doing a trial when you randomize people.

SIEGEL: Well, Dr. Fauci, thank you very much.

Dr. FAUCI: You're quite welcome.

SIEGEL: This one - again is Dr. Anthony Fauci, AIDS researcher himself and director of the National Institute of Allergy and Infectious Diseases.

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