Tenofovir as a Microbicide Gel: Where are sex workers in the CAPRISA calculations ?

31/08/2010 at 08:22 Leave a comment

By Cheryl Overs

The Caprisa microbicide trial session may have been the most important session of the conference. The trial tested the efficacy in preventing HIV and herpes and the safety of a gel that contains 1% of an antiretroviral drug called Tenofovir.

To cut a  long story short the research claims that a vaginal microbicide might prevent transmission of HIV during unprotected sex by somewhere between 39%.and 50%. This news received a standing ovation in the 1200 seat session room and among the other 1500 watching live feeds.  We heard a lot about the potential benefits to women in Africa who are faithful to HIV infected husbands. There were even calls to ‘roll it out now’ to prevent more infections among this group despite there being virtually no information available about what impact a partially effective microbicide might have on women who have many partners with whom they have anal and oral sex as well as vaginal sex.

For sex workers of all genders a non contraceptive gel that gives some protection from HIV in vaginal sex but not oral or anal and does not  protect against STIs clearly has the potential to be a disaster. I have written extensively about this in the Sex Work and the New Era of Prevention and Care http://www.plri.org.

The researchers are confident that  trial was ethical because it meets UNAIDS guidelines for such trials but some delegates were not so sure.A delegate from Kenya questioned both the ethics of the trial and results on his blog http://hivinkenya.blogspot.com/. He said it’s hard to know exactly how to interpret the results of this trial because the research seems to be incomplete in many ways.

“[According to the study] women who used the gel more consistently were much less likely to be infected…”. But women using the gel more consistently also had less sex. And those having more sex tended to use the gel less consistently. Also the trial has not established if partners were infected or uninfected. So we don’t know if the vaginal gel has achieved this, or exactly what it has achieved.

Can we say clearly that the results of the trial could not have been due to chance? Technically, the result is statistically significant, other things being equal. But we just don’t know enough (or are not being told enough). The paper notes that, “Overall, condoms were reportedly used in 80.3% of sex acts; increasing from 78.5% in the first 6 months to 84.3% in months 18-24”. This means that as condom use went up, the efficacy of the gel seemed to go down.

The paper goes on “we observed declining HIV incidence rates in the placebo gel arm. This may have been due to their declining coital frequency and increasing condom use.” So, are they saying that over time, the efficacy of the placebo gel increased as the efficacy of the Tenofovir gel decreased? That seems like a strange result. If the trial had gone on for five years, would these two trends have continued? Not only is the trial questionable ethically, it is also of questionable validity.

According to John R Talbott of the Huffington Post “The Vienna Conference has pushed the Tenofovir gel trial as a great breakthrough and the press have bounced the story around the world (and the www). The authors of the paper may well be regretting that their work has been chosen to be hyped above all others this time around. They, of all people, are probably painfully aware that we are still a long way from a pharmaceutical product that will have a significant impact on HIV transmission.

The trial itself is quite tentative, involving a small number of people. And the scope of the research was very narrow. One of the most shocking things is how high incidence is, in both the intervention (5.6%) and the control (9.1%) groups. If you had hundreds of people whose sexual behaviour you were studying, you might want to investigate their sexual behaviour. This trial didn’t really do that. They didn’t test the participants’ partners. They don’t even know if those who contracted HIV did so through sexual behaviour! Or, if they did check the partners, they don’t mention this in the paper.

Another extraordinary thing about the trial is that condom use was high and steady throughout the trial, in both intervention and control groups. Condom manufacturers must be wondering exactly what the participants did with the condoms to have such poor results with them.

Over the trial period, the number of sex acts involved was not particularly high. Even if none of the participants had used condoms, incidence of between 5.6 and 9.1% would be hard to explain. The authors speculate about the women having sex with ‘migrant workers’ but they don’t say if the women did so. The trial selected women that were at low risk of being infected with HIV, so why did so many turn out to be at high risk?

Not only did the women in the trial not have sex particularly often but they had sex less and less often as the trial went on. The number of sex acts per month went from 7.2 to 3.1 per month. The more people were having sex, the less likely they were to use the gel and those who were having sex least frequently were the most likely to use the gel. But frequency of sex doesn’t seem to change the risk of becoming infected. It’s as if sexual behavior is not especially relevant to the results of the trial.”

The trial could be unethical because the researchers would have known in advance, or should have known in advance, that at least some HIV is transmitted non-sexually. Yet they made no effort to protect people from this. Nor did they make any effort to inform people that such a risk exists. And the results are of questionable validity because we don’t know how people became infected and, therefore, why some people didn’t become infected. There could have been many factors that increased the risk of infection and others that decreased the risk. Tenofovir gel may have had some effect, but we don’t know what effect it had or why it had an effect.” Was the Tenofovir Gel Microbicide Trial Ethical? http://hivinkenya.blogspot.com/.

These issues may explain the researchers’ position that this study only takes the idea of a vaginal topical ARV based microbicide to ‘proof of concept’ stage. As I understand it shows that there is something worth researching there. But that didn’t stop people calling for immediate roll out of this imagined magic bullet.

The discourse about potential benefits of a vaginal microbicide are openly modelled on, and aimed at, women who cannot make the men to whom they are faithful use condoms and to preserving sexual pleasure for those men. Taking the Caprisa study results as an accurate indication that the likely efficacy of a vaginal microbicide against HIV and herpes is likely to be about 50% – and allowing for dramatic improvements that take efficacy to say 70% – the potential impact of such a product coming on the market could be devastating for sex workers and clients.  So much rests on whether or not condoms are abandoned. Its obviious and inevtiable that massive condom abandonment will happen in commercial sex.  Can you imagine trying to talk a client into using a condom when they all know a gel is available ?  Sex business operators are sure to want to meet that demand.

No information appears to be available about whether a microbicide could also prevent pregnancy STIs or oral and anal transmission of HIV.  If not it is even more worrying that sex workers health outcomes will be worsened rather than improved by a microbicide.

There are similar issues about the value of PREP and  ‘treatment as prevention’. As one delegate said, “It will not fail because the drugs don’t work, they do. But most people have not been tested; others refuse to take the drugs; others don’t have access to the drugs; and others still take the drugs but they don’t work. And while this is going on, far too many people are still being infected with HIV.”

The thirst for a neat technical fix to replace the messy imprecise art of prevention at the conference was chilling. The ‘Aids community’ is as ready to believe in the magic gel as clients and brothel owners will be when they get wind of it.. Much,  much more thinking needs to be done about the microbicide  – much more.

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Entry filed under: research.

Reflections on AIDS 2010 Cheryl Overs I AM SICK OF HEARING ABOUT SAFE RAPE

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