The Centers for Disease Control and Prevention (CDC) has published an interim guidance for health care providers regarding pre-exposure prophylaxis (PrEP) for high-risk individuals. The guidance comes on the heels of data released late last year, concluding that daily use of Truvada (tenofovir and emtricitabine) among HIV-negative men who have sex with men (MSM) reduced new HIV infections by about 44 percent.

That data, from the iPrEx study, which took place predominantly in Peru, Ecuador and Brazil among HIV-negative MSM and transgender women who have sex with men, generated tremendous press coverage. Aside from the modest level of protection found overall, the study also revealed that in people who reported taking Truvada at least 90 percent of the time, the reduction in infections was 73 percent.

In the interim guidance, published January 27 in the Morbidity and Mortality Weekly Report (MMWR), the CDC warns, however, that there are important caveats to the study results—limitations that many community members pointed out when the data were first published.

These include the fact that less than 10 percent of the participants resided in the United States. This means we don’t yet know whether or to what extent PrEP will work in the high-risk populations in this country. Moreover, adherence rates were poor in the study, and drug-level testing in a subset of people suggested that self-reported adherence—combined with pill counts and pharmacy records—was a poor indicator of actual adherence. Other concerns include the long-term safety and efficacy of PrEP and the fact that we don’t know how people’s sexual behavior will change when they use PrEP in real-world settings.

More detailed guidelines from the CDC and the Public Health Service (PHS) are in the works and expected to be released in the coming months. Given the fear that providers are already beginning to prescribe Truvada for PrEP—a drug that is readily available by a prescription at any pharmacy—the CDC has rushed to provide an interim guidance for those providers.

Before providers prescribe PrEP, the CDC is recommending that they conduct a thorough assessment of a person’s HIV risk behaviors and that they document ongoing high-risk activity. An HIV test (a more sensitive test to determine a recent infection may be used in those with symptoms) and tests for sexual transmitted infections (STIs) are recommended. So too are tests for kidney function—the tenofovir in Truvada is associated with kidney toxicity—and hepatitis B virus (HBV) infection, given that Truvada is also active against HBV and must be used cautiously.

Providers are cautioned to prescribe no more than a 90-day supply of PrEP and to offer extensive HIV risk-reduction counseling, adherence counseling and condoms.

Follow-up is recommended every two to three months to test again for HIV. Further assessments are also recommended at this time for adherence and continued HIV risk behavior, and to provide ongoing support and counseling for these. Kidney function testing is again recommended three months after a person first starts PrEP and yearly thereafter. Tests for common STIs are also recommended every six months, even if a person has no symptoms.

The CDC also recommends that before people discontinue PrEP—whether because of safety concerns, a positive HIV test result, or a person requests to stop treatment—their providers should link them to HIV care (if a person has become infected) or ongoing HIV risk-reduction counseling and support. For people who have HBV, their providers should also discuss whether to continue treatment as a means to control HBV infection.

The full list of recommendations can be found here.

To learn more about the community’s response to the iPrEx results, and to participate in discussions about next steps, visit the website of the HIV Prevention Justice Alliance here.