The Future of HIV Prevention
Dr. Kenneth Mayer
Let's face it, a cure for HIV remains far from imminent. So prevention is the best hope to control the epidemic in the here and now. While we've enjoyed plenty of good news about the effectiveness of PrEP, microbicide gels and circumcision over the last few years, what's next?
That was the topic of Kenneth Mayer, M.D.'s plenary Thursday in Melbourne. He is a clinician in Boston and professor at Harvard Medical School. Here, with Dr. Mayer's help, we take a look at HIV prevention and discuss, where we are and where we're headed:
Pre-Exposure Prophylaxis (PrEP)
The Facts
Pre-exposure prophylaxis, or PrEP, is a way for people who do not have HIV but who are at risk of getting it to prevent HIV infection by taking a pill every day. When someone is exposed to HIV through sex or injection drug use, these medicines can work to keep the virus from establishing a permanent infection. When taken consistently, PrEP has been shown to reduce the risk of HIV infection in people who are at high risk by up to 92 percent.
The Concerns
PrEP is much less effective if not taken consistently, and works best combined with condoms. "We do know that oral prophylaxis may be appropriate for some individuals," says Dr. Mayer. "But it involves individual education and ongoing support. "
Prep is also expensive: About $800 a month (wholesale) in the U.S. Plus, many people, especially heterosexual women and men, aren't really aware of it. Still, the worry that it would lead to increased risk behavior was dashed at this week at AIDS2014. A study showed that those who take the pill aren't turning into sexual risk takers because they feel protected.
What's Next?
Experts are exploring whether less frequent dosing—a different pill that might be taken less often—might increase adherence. And several studies are looking at replacing the pill with a monthly (or less often) injection of anti-HIV medication. Early trials have shown the shot to be safe and effective. For women, the injection could also be formulated to prevent both HIV and pregnancy down the road.
Treatment as Prevention
The Facts
In May 2011, a groundbreaking study offered conclusive evidence that treating HIV positive people with anti-AIDS medication prevents transmission of HIV to their uninfected partners. In other words, treating the infected also reduced infectiousness. Win-win.
The Concerns
Treatment as prevention works best for discordant couples (one partner is HIV positive, the other isn't) in stable, monogamous relationships. However, of the 35 million HIV-positive people worldwide, 19 million of them don't know that they have the virus, according to UNAIDS. About 16 percent of HIV positive Americans don't know they have been infected.
"Even in the best case projections, by itself, treatment expansion by isn't going to be sufficient if we really want to arrest the epidemic as soon as possible," notes Dr. Mayer.
What's Next?
Continue to scale up testing and access to treatment.
Microbicide Gel
The Facts
Several years ago, a landmark study showed that antiretroviral microbicides in gel form could prevent sexually acquired HIV infection in women. Unlike condoms, tenofovir gel is the first HIV prevention technology that women can control themselves and enables women to take charge of their HIV risk. It also protects against herpes.
The Concerns
The gel hasn't been approved by the U.S. Food and Drug Administration and so is not yet available. The next step: The results of a second trial, confirming the gel's effectiveness, are due next year. "With the confirmatory study underway, 2015 could be a major game changer," says Dr. Mayer. "If we corroborate a gel being effective in two studies, this would lead toward licensure."
What's Next?
Scientists are looking at several other gels, which would provide women with even more options. A study of 360 MSM and transgender women is exploring whether the gel prevents the spread of HIV during anal sex. And University of Pittsburgh scientists are exploring the use of a dissolvable film—similar to a Listerine breath strip—that is easier to store and less messy than gel, and can be inserted in the vagina without an applicator.
Microbicide Rings
The Facts
Microbicide or vaginal rings are similar to birth control rings already on the market, and deliver antiretroviral medication slowly over time. The rings are easy to use, woman-controlled and offer effective, sustained protection against HIV infection and herpes.
The Concerns
The ring is not on the market.
What's Next?
Two studies underway in Africa, with results about the effectiveness of the vaginal ring against HIV are due by 2016. The device also has the potential to deliver contraceptive hormones, so women would be protected against both HIV and pregnancy. What's more, scientists are looking into a "one size fits most" diaphragm that would contain anti-HIV medication and act as a barrier against pregnancy.
Circumcision
The Facts
Voluntary male circumcision has been shown to reduce the risk of heterosexually acquired HIV infection in men by approximately 60 percent. Its greatest advantage: it's a one-off procedure, with no ongoing costs or issues to worry about. Once a boy or man has undergone the procedure he will benefit from the preventive effect for the rest of his life.
The Concerns
Sixty percent is far from 100, so circumcision is only a partial solution. In the United States and many other developed countries, most men are already circumcised, so Africa has been the major target for this intervention. Plus, it only protects men, and doesn't lower a woman's risk of contracting the virus. It also hasn't been shown to be effective in MSM in the "receptive" role.
What's Next?
"Down the pike, we'll be looking at new approaches that don't involve extensive surgery," says Dr. Mayer, who adds that they will be less painful and more efficient. Also in Africa especially, many health professional are being trained to perform circumcisions, rather than just doctors.
At the end of his lecture, Dr. Mayer concluded, "we talked about a lot of exciting things, but they are not quite magic bullets. Still, if we attend to these things, we may be able to achieve the end of the epidemic that we look for.
While he hasn't given up hope on a vaccine, in the meantime, he added, "we already have multipurpose prevention technology: It's called a condom."
Linda Villarosa runs the journalism program at City College in Harlem and writes frequently about health and social issues. This is the sixth International AIDS conference she has attended as a volunteer reporter. Follow her on Twitter @lindavillarosa.