25/09/09

HIV vaccines: the ecstasy and the agony

How excited should we be about the results of the HIV vaccine trial in Thailand? I argued in The Times today that the results are the worst type of good news. The combination vaccine is good enough to raise real hopes that we can find something that works. After the gloom of last year, that’s no small thing. But even Vaccine Cheerleader-in-Chief Anthony Fauci is circumspect about yesterday’s announcement. (NPR interviews Anthony Fauci here)

There a couple of things that no-one much has mentioned. The first is that the vaccine was designed to produce a response to sub-types E and B. Subtype E (and an AE recombinant) is a form of HIV-1 that is very common in heterosexual HIV infections in Thailand, but much less common in other parts of the world. In most Western epidemics (and among gay men in other parts of the world, including Thailand) subtype B is most common. But as you can see on the map, in east and southern Africa, where around half of people with HIV in the world live, subtype C has the upper hand.

clademap

So even if we improve the efficacy of the combination that was tried in Thailand, there’s no telling whether it will be useable in Africa, where it is most needed.

Second, those who got the real vaccine combination but went on to get infected with HIV anyway had just the same amount of virus in their blood, on average, as those who got the placebo injections. This was a surprise; researchers had hoped that people who had been vaccinated would at least have lower concentrations of virus. It was also a disappointment, because lower viral loads generally mean less damage to the immune system (which in turn means it takes longer to get sick from other things, or to develop AIDS). Lower viral loads also mean that an infected person is less likely to pass HIV on to other people.

Some of the better scientific analyses (such as this report from IAVI) raise questions about just how robust the results will turn out to be once they are analysed more carefully. Interestingly to epi-nerds, none of the press releases or official fact sheets about the trial gave a p-value — a measure of the probablility that the difference between the two groups was due to chance. It fell the the ever-reliable Jon Cohen at Science to dig that out (and to Roger to find it for me at a bleary-eyed hour; thanks.)

It’s always easier to pick holes in these trials than to do them; whatever the results, the Thai Ministry of Public Health and the US Army deserve credit for having had the balls to push ahead with this difficult and much criticised piece of research.

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This post was published on 25/09/09 in Science.

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4 comments

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  1. Comment by Richard Marcus, 25/09/09, 01:15:

    After watching friends and colleagues die throughout the 1980’s of mysterious and unknown causes – at least according to their obituaries – I’ve become horribly cynical about any of the so-called advances in HIV/AIDS research that would in any shape or form that would reduce prevention. The first thought I had upon seeing the news of this vaccine, was great, now people are going to start thinking they’re immune and all the work that’s been done over the years on education and prevention will fly out the window. The conservative religious right will pounce on this to prevent even less money be spent on programs teaching people about safe sex, because now of course it will no longer be needed. This is just the sort of thing that could cause an upsurge in the epidemic.

    The other question to ask is how long will it take the virus to mutate and become immune to the vaccine? As Elizabeth points out it already doesn’t work on the most common strain in Africa. All one needs do is think about the fact that viruses and bacterial infections routinely build up resistance to vaccines and antibiotics to question how long a vaccine will actually be effective.

    We must keep up the fight for adequate funding for preventative measures – they are the only sure fire way of stopping the disease.

  2. Comment by Daniel Reeders, 28/09/09, 02:23:

    Hmm. Take two on trying to participate in a discussion with your blog on this topic… ERV, a genetic scientist and blogger I love, has written about the vaccine *strategy* used in Thailand (http://scienceblogs.com/erv/2009/09/prime–boost_a_viable_hiv-1_va.php) and this suggests the second specific protein component of the one-two punch could be customised to include more/different HIV sub-types.

  3. Comment by peripheries, 10/10/09, 08:40:

    Considering that the results are clearly not significant in the per-protocol analysis …

    http://online.wsj.com/article/SB125511780864976689.html

    All of that is a bit academic, in a more sinister sense… How did they decide to let the hype built knowing that it was NS?

  4. Comment by Deusdedit Ruhangariyo, 17/07/10, 06:41:

    Your presentation yesterday at the Journalist 2 Journalist training was terrific.

    It really made my day. Together let us join hands to fight the AIDS Mafias.

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