New guidelines from the U.S. Preventive Services Task Force USPSTF recommend offering pre-exposure prophylaxis PrEP for the prevention of HIV infection in persons at high risk of HIV acquisition. The new recommendations received a category A endorsement — indicating that there is high certainty that the net benefit is substantial.
Despite advances both in the treatment and prevention of HIV infection, an estimated . million Americans — approximately .% of the population — are currently infected, and each year almost , new individuals acquire HIV. Most of those who become infected fall into high-risk categories, such as those who engage in high-risk sexual behavior or injection drug use.
Rigorous randomized trials have established that PrEP can substantially reduce the risk of HIV acquisition. In one landmark trial involving , seronegative HIV men who have sex with men, PrEP with combination emtricitabine and tenofovir reduced the incidence of HIV acquisition from .% in the placebo group to .% in the PrEP group over a median of . years caveat: the benefits among a small subset of patients enrolled for . years were more modest, with an HIV incidence of approximately % in the control group vs .% in the PrEP group. In another trial involving HIV-serodiscordant heterosexual couples from Kenya and Uganda, combination tenofovir-emtricitabine lowered the incidence of HIV infection over a -month period from . per per year in the placebo group to . per per year in the treatment group. Rigorous trials have even demonstrated the benefits of intermittent PrEP coupled with post-exposure therapy. Clearly, use of PrEP can lower rates of HIV transmission, and it should have an important role in preventing the spread of this challenging disease.
However, we worry that the benefits of PrEP have been exaggerated, likely in a well-meaning effort to encourage increased prescribing and access to prophylactic medications. This recent New York Times article, for example, claims that even without the use of condoms — PrEP is close to percent effective at preventing contraction of H.I.V. This is a dangerous misconception. Although PrEP is an effective preventive service, it is far from perfect. As can be seen from the trial data described above, PrEP lowers, but does not eliminate the risk of HIV transmission. Even in the experimental settings described above, the annual rates of HIV acquisition ranged from approximately in to in . This means that over the course of years, %-% of high-risk individuals will become infected with HIV even in spite of PrEP therapy.
Experts from the CDC estimate that with perfect compliance, PrEP therapy is % efficacious. But even this may be misleading. In real-world settings, we suspect that actual compliance with PrEP is likely to be inconsistent, and effectiveness rates are likely to be lower, not higher, than those reported in the rigorous trials described above. Without appropriate counseling about the shortcomings of PrEP, it might offer a false sense of security, leading to higher rates of risky behavior, counterbalancing the benefits.
In the same vein, there is growing evidence that the use of PrEP may be correlated with higher rates of contracting other STIs, presumably because PrEP may cause some users to be less vigilant about barrier protection. One recent analysis demonstrated a significant increase in the incidence of STIs among gay and bisexual men who began using PrEP. Again, it is imperative that we counsel our patients that PrEP will not protect them from other STIs.
Finally, we would be remiss if we did not highlight the potential adverse effects of PrEP, such as low bone density, headaches, weight changes, and possibly even some adverse renal effects. For those at high risk for HIV, these adverse effects pale in comparison to the benefits. But for those with low to moderate risk, the calculation is less clear cut.
Overall, we strongly support the new USPSTF to promote PrEP for all high-risk patients. Still, in promoting PrEP to our patients, it is critical to counsel them that the treatment is far from perfect. If they do opt to take PrEP therapy, it is important that they take the medication every day as prescribed; if not, the treatment s effectiveness will rapidly drop. Even with perfect compliance, given the high stakes, we will continue to recommend barrier protection with condoms, which are about % effective in preventing HIV, both to protect against other STIs, but more importantly to reduce the residual risk of HIV acquisition despite PrEP treatment. While we strongly support the new PrEP guidelines from the USPSTF, because of these caveats and the risk for unintended consequences, Slow Medicine would have preferred to see greater emphasis in the new recommendations on barrier protection with condoms, in addition to PrEP, for lowering HIV risk.
Michael Hochman, MD, MPH, directs the Gehr Center for Health Systems Science at the University of Southern California s Keck School of Medicine. Pieter Cohen, MD, is a general internist at Cambridge Health Alliance in Somerville, Massachusetts, and associate professor of medicine at Harvard Medical School.
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