Using Antiretrovirals to Prevent New Infections

Mark Chataway is co-chairman of Baird’s CMC, a Mapping Pathways partner organisation. Here, he outlines the various prevention strategies.

I have been involved in fighting AIDS since 1983. I was the first full-time communications director of an AIDS organisation in the US. At the time, none of us imagined how terrible the epidemic would get – I remember a time when most of my colleagues thought that only people who had had over 100 sexual partners a year were at risk.

Like most people who’ve been so close to the epidemic, I often lose sight of how much progress we have made. The epidemic peaked long ago and the number of cases is falling every year. That is the kind of public health success that has not often been seen in the modern era. We are most of the way towards eliminating AIDS in the industrialised world although shocking epidemics still exist in many developing countries. There are still a tragically large number of caofses in Southern and Eastern Africa and the threat of HIV breaking out at-risk communities persists in parts of Asia and maybe even Eastern Europe.

There is a threat – still distant but definitely visible – that we will lose this astonishing success through complacency. Very few of us realised how fast we could cripple the epidemic once we started treatment. A few of us risk forgetting how fast the epidemic will bounce back if we allow treatment rates to slip.

We can make AIDS rare – and eliminate it entirely from rich countries – using technologies that we already have. The question is whether we have the will to do it.

There are three promising strategies for using the medicines we have as prevention.

1. Treat enough HIV-positive people with antiretroviral medication, in an effective manner: If we improved access to treatment for people living with HIV, including the offer of treatment earlier in the course of the disease, there is evidence that the “community viral load” would fall. Providing effective treatment to more individuals with HIV can reduce onward infections in a community because people on treatment are less likely to transmit the virus. The chances of HIV-negative people becoming infected would reduce progressively over time. An approach that focuses on improving access to care and antiretrovirals is sometimes called TLC+ (testing, linkage to care, plus treatment).
2. Provide antiretroviral medication for HIV-negative people who are at high risk of infection: Some HIV-negative people at the highest risk of being infected by HIV cannot modify their risk of being exposed. For example, sex workers may be unable to persuade their clients to use condoms and intravenous drug users may not have access to clean needles. For many of them, stopping the underlying risk behaviour – sex work or drug use in these examples – is not feasible. These HIV-negative people, at very high risk of infection, can be offered antiretroviral medicines to lower their chances of becoming infected in the future. They would have to take these medicines routinely and they would still be at some, albeit lower, risk of becoming infected if they could not avoid risky behavior. This approach is usually called pre-exposure prohphylaxis (PrEP). Recent trials have shown that PrEP can reduce the risk of infection significantly in gay men although puzzling findings suggest that they may not protect women.
3. Provide topical, antiretroviral-based microbicides to HIV-negative people: Antiretrovirals could be used topically – in a gel or lubricant formulation, for example – in the vagina or the rectum by HIV-negative people. The topical medicine could reduce the risk of HIV acquisition. This approach is often called microbicides or topical PrEP. A recent study in South Africa proved that the concept works and showed a degree of efficacy in protecting women from infection. Other studies have provided encouraging data on rectal and vaginal products.

Some behaviour change efforts have worked well – especially those run by affected communities for their own vulnerable people. Many behaviour change efforts barely worked at all but continue to be funded because there have been no alternatives. (Evaluation of individual efforts will always be complex – see, for example, the extended debate over the evaluation of the LoveLife programme in South Africa – but Northern Europe is an interesting example: countries such as Belgium, the Netherlands and the UK followed very different behavioural interventions but all have ended up with very similar epidemics.) Money from under-performing programmes can be re-directed to prevention efforts that have been proven to be effective in well-controlled prospective trials. Effective prevention, of course, reduces the need for treatment in the medium to long term.

My colleague, Jim Pickett, uses car safety as an analogy: nothing can take the place of safe, skilled driving but seat belts, air bags and better car design have reduced the number and severity of accidents dramatically, even as the number of cars and drivers has increased. These three approaches to using antiretrovirals might be the air bags, seat belts and safety frames of the HIV epidemic.

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