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Thai trial gives HIV hope

Shane McLeod reported this story on Friday, September 25, 2009 12:30:00

SHANE MCLEOD: There's new hope in the scientific research community with a breakthrough in
developing a vaccine to protect against the virus that causes AIDS/HIV.

A trial of an experimental vaccine in Thailand has found it reduced the risk of contracting the
virus by almost a third.

More than 16,000 volunteers took part in the study. It involved a combination of two previously
ineffective vaccines, giving researchers around the world new hope that a vaccine against the virus
may actually be achievable.

Among them is Professor Andrew Grulich, the head of epidemiology and prevention programs at the
University of New South Wales national HIV research centre.

ANDREW GRULICH: Look, it really is a substantial breakthrough because research in the HIV vaccine
field of late has been really very pessimistic. The recent studies in this field have been entirely
negative and have led to speculation that an HIV vaccine may actually be impossible.

So what this result adds, while it's not a tremendously strong result, it really reinvigorates hope
in the field of HIV vaccine research.

SHANE MCLEOD: What have the researchers done in this trial that they haven't done before?

ANDREW GRULICH: Well look this was a very large-scale trial of a vaccine strategy in Thailand. They
combined two very different vaccines. The intervention included part of the coat of HIV, if you
like, a protein called gp120, as well as a bird virus, canary pox, producing HIV proteins. And
those two were combined together.

And the rather surprising this was that those two trailed on their own have previously shown not
much hope in preventing HIV infection. So perhaps it's some aspect of this combination that's led
to this result.

SHANE MCLEOD: Do they have any theory on why this has worked where they haven't separately?

ANDREW GRULICH: Look we don't have the theories yet. It's important to point out that we don't know
the full results yet, that these results have just been released at a press conference and haven't
been reported scientifically yet.

That will happen next month and there will be tremendous scientific interest in finding out the
full results and particularly in teasing out why this vaccine might be working.

SHANE MCLEOD: In terms of the size of this study it involved 16,000 people in some of the highest
risk areas in Thailand. Is it enough of a sample size to be fairly confident about the results?

ANDREW GRULICH: Well we're told by the researchers that this, almost one-third reduction is a
statistically significant reduction but the details of that have not yet been reported. So we need
to wait until those results are reported next month to be entirely certain about that.

But nevertheless a significant reduction is something we have never seen in HIV vaccine research,
so that's really why this result is creating such excitement.

SHANE MCLEOD: And a vaccine for HIV, it would seem to be the holy grail in epidemiology. Is it
something that scientists have thought was possible?

ANDREW GRULICH: Well you know this goes back a long way. And in fact in the mid-1980s, a United
States secretary of health famously said that she thought that they would have an HIV vaccine
within two years, so there's been hope because of course we have vaccines against so many
infectious agents.

But really, since the mid-1980s the 25-odd years of research have been mostly very disappointing.
We've seen some promise in experiments in monkeys but really no evidence until this one that a
vaccine might be protective in humans.

SHANE MCLEOD: And if a vaccine becomes I guess more possible, does that have an impact on efforts
to prevent people contracting HIV?

ANDREW GRULICH: Well look one thing we need to be very certain about that even if these results are
completely confirmed, a 30 per cent effective vaccine is not a lot of help because it's only 30 per
cent effective.

If people then feel that they are protected against HIV and take more risky behaviour then it's
quite possible that increasing risk behaviour would overwhelm the protective effect of the vaccine
and actually lead to an increase in infection.

So this is not the end of the road by any means but it's really opening the door to hope, if you
like. And scientists in this field will be watching the presentation of these results in the next
month with really great interest.

SHANE MCLEOD: And hearing this news, what sort of mood do you think there will be in the research
area now?

ANDREW GRULICH: Well you know the vaccine research of the last three years or so has been very
pessimistic because the last major trial in this area, called the STEP trial was of a vaccine that
looked very promising in the laboratory and was entirely ineffective in humans and in fact in a
subset may have even increased the risk of HIV infection.

So this will change the mood from a rather pessimistic one to an optimistic one I hope, depending
of course on the full presentation of these results which we'll be keenly waiting on.

SHANE MCLEOD: Professor Andrew Grulich from the National Centre in HIV Epidemiology and Clinical
Research at the University of New South Wales.