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PrEParing for Big News: The Future of HIV Prevention?

2010 November 22

Tomorrow, the New England Journal of Medicine is to publish the results of a study on the potential of Pre-exposure Prophylaxis (PrEP) in preventing HIV transmission among so-called “high-risk groups.”  The idea is that, by providing a daily dose of the drug Truvada – an anti-retroviral (ARV) therapy often given to HIV+ individuals, and consisting of the drugs tenofovir and emtricitabine – to, say, a commercial sex worker, her risk of sexually contracting the virus is lowered.  While I am very excited to see the results of the new study, I am also worried about what they could mean for the funding of HIV treatment and prevention around the world.

I am very much a believer in the “prevention is the best medicine” approach to public health.  However, over the past 30 years, HIV/AIDS has challenged every single public health paradigm.  Because much of the world lacks comprehensive, evidence-based prevention programs, HIV continues to infect millions of people.  Anti-retroviral therapy (ART) has given hope and longevity to millions living with HIV, and could become the future of prevention.  But what does this mean for HIV+ people living in countries like Botswana, where one of the PrEP trials has been underway for almost a year?  (NB: this study has undergone a shift in focus due to a surprisingly low rate of new infections, due to a confluence of factors.)  Outside of a well-funded study, Botswana probably could not afford PrEP.

In these times of economic hardship, there is already criticism of governments that are allotting fewer and fewer funds to HIV/AIDS domestically and internationally.  Across the US, AIDS Drug Assistance Programs, which provide ART to HIV/AIDS patients who cannot afford their medications, are in danger.  Budgets for malaria and diarrhea are increasing (as they should be), while the HIV/AIDS piece of the pie shrinks (the problem keeps growing, so should the budget).  But since we know we’re working with finite resources, finding a balance in funding prevention and treatment is hard.  Very hard.

ART is expensive, and it’s a lifetime commitment, so costs continue to climb as more and more people need the drugs, and stay on them for 30, 40, or 50 years.  Prevention tends to be cheaper (condoms, clean needles, and other harm reduction methods, for example) than treatment, but PrEP will no doubt be expensive.  For one thing, the patient does not receive a single dose (as is the practice for preventing HIV transmission by pregnant women during childbirth), but rather a daily regimen.  This regimen requires strict adherence by patients- a very high standard to set, especially in places like rural Botswana.  However, there is evidence so far that PrEP, when combined with other prevention methods such as monogamy and condoms, might be effective.  This is indeed hopeful, but it is pragmatic?

Post-exposure prophylaxis (PEP) has been accepted practice for years in treating patients who may have been exposed to HIV in the previous 72 hours, via needlesick, unprotected sex, rape, etc.  Of course, this is a last resort, and generally requires a serious threat that the “source individual” is HIV+, the patient in question is HIV-, and there is significant risk based on the incident.  The drugs must be taken for the next 28 days, during which patients may experience extreme side effects both from the drugs themselves, and from interactions with other medications.  Because PEP is meant to be a one-time, Plan B-type intervention, it naturally gave rise to the idea of PrEP.  (Wouldn’t it be crazy if Plan-B Emergency Contraception came first and then inspired “the pill”?)

In their article “Before and After: PEP and PrEP”, authors Luis Scaccabarozzi and Mark Milano articulate some of my concerns about PrEP:

Four PrEP trials have been stopped before completion for very different reasons. Studies in Cambodia and Cameroon were stopped when activists protested that adequate safer sex counseling was not being provided and that little or no planning was in place to provide healthcare for those who seroconverted during the trial. The Malawi Ministry of Health ended a trial because of concerns that widespread use of tenofovir could complicate its use as an HIV treatment, and a trial in Nigeria was shut down due to questions about trial sites’ capacity to conduct the study.

Questions have also been raised about the populations being studied. We know from experience in countries like Thailand that government enforcement of condom use in brothels can dramatically lower HIV infection rates. So is it ethical to conduct studies in sex workers when we already have a method proven to work? In particular, is it ethical to conduct studies in injection drug users in countries where clean needles are not provided by the government? These concerns and others have been the subject of heated debate.

They further point out that “Community activists are balancing two contradictory needs. Advocacy is needed to ensure these new prevention ideas are funded appropriately and tested ethically. But it’s important not to raise expectations for interventions that may not work, that may prove no more popular than condoms, or that may do harm if used inappropriately.”  One of these “inappropriate” uses sited in at least one article I read cited instances of gay men taking a dose of the drug tenofovir before engaging in risk behavior, or mixing the ARV drugs with methamphetamines and Viagra.

An article on Avert.org, states:

…it has been argued that theoretically pre-exposure prophylaxis could have an enormous impact on the worldwide HIV-1 epidemic. Mathematical models estimate that if tenofovir PrEP was used by 90 percent of high-risk people and was effective 90 percent of the time, potentially the spread of HIV infection could be reduced by more than 80 percent in a few years.  For sub-Saharan Africa, it is estimated that approximately 2.7 million to 3.2 million new HIV-1 infections could be prevented over the next ten years by using PrEP and preventing high-risk behaviours among the most sexually active population groups.

HIV/AIDS activists are certainly familiar with big expectations, and big let-downs.  My biggest question about the potential of PrEP as an international intervention is still the cost.  While this is being tested across South America, Africa, and the US, it is highly unlikely that the majority of the countries involved would be able to afford its large-scale implementation.  The US and Brazil are the likely exceptions.  And are international health experts suddenly going to put all of their eggs in the PrEP basket?  What will happen to funding for condom campaigns, needle-exchange programs, and comprehensive sex-ed?  PrEP, should it prove effective in reducing HIV transmission, should be carefully evaluated before being added to the ever-growing arsenal of HIV prevention methods.  But in no way should it eclipse the much cheaper, easier-to-use, and already proven harm-reduction methods like condoms and clean needles.



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