A gay man who consistently took PrEP (pre-exposure prophylaxis) for two years has become infected with HIV, a Canadian scientist reported Thursday at the Conference on Retroviruses and Opportunistic Infections in Boston.

PrEP is a combination of two HIV medicines (tenofovir and emtricitabine) sold under the name Truvada. As described by AIDS.gov, PrEP “is a way for people who don’t have HIV but who are at very high risk of getting it to prevent HIV infection by taking a pill every day.” Studies have shown this medication to be highly effective, with daily use of PrEP lowering the risk of an HIV infection by 92 percent, according to the Centers for Disease Control and Prevention.

“To our knowledge, this is the first reported case of breakthrough HIV infection with evidence of long-term adherence to [Truvada],” said Dr. David Knox, an HIV specialist at the Maple Leaf Medical Clinic and lead author of the new study.

In his presentation, Knox noted the patient was a 43-year-old gay man, a regular at the Maple Leaf clinic who regularly got tested for HIV. In April 2013, following a suggestion he start PrEP, the man began the regimen. According to Knox, the patient's HIV-positive partner was on antiretroviral therapy with "undetectable" levels. Yet the man also reported “multiple acts of anal receptive sex with casual partners without the use of condoms” occurring within two to six weeks of testing positive for HIV.

PrEP is known to be less effective when taken inconsistently. However, the patient was “adamant” about his adherence to the drug regimen, while both pharmacy records and dried blood spot analysis indicated “consistent dose-taking in the preceding one to two months,” said Knox.

“Failure of PrEP in this case was likely due to the transmission of a PrEP-resistant, multi-class resistant strain of HIV 1,” said Knox. As one conference attendee suggested, these findings are likely to be misconstrued, and, indeed, controversy has surrounded the blue pill from the start.

To PrEP or Not to PrEP

Since its Food and Drug Administration approval in 2012, Truvada has stirred ambivalent feelings within the gay community and that is reflected in uptake of the drug. Today estimates suggest less than 30,000 Americans take PrEP — just one-twentieth of those who might benefit from the drug, according to NAM, a national AIDS organization. Since the AIDS crisis years beginning in the 1980s, gay men have been calling for drugs, so for many, this response is confusing.

In an 2014 interview with Out Magazine, for example, actor Zachary Quinto candidly discusses PrEP, stating, “We need to be really vigilant and open about the fact that these drugs are not to be taken to increase our ability to have recreational sex… and we don’t yet know enough about this vein of medication to see where it’ll take us down the line.” Quinto is far from alone. Others in the gay community also caution the drug does not delete all the dangers of sex, as Out reports, while some say those taking the pill practice “riskier” sex, avoiding personal responsibility.

Angry disputes follow each and every airing of concern, no matter how valid a criticism proves to be. As Mark Joseph Stern notes in this blog post on Slate, the problem may lie in a “generational dispute” between older gay men, who witnessed countless deaths during the days of crisis, and younger gay men, “who often see HIV as little more than a chronic but manageable disease.” Undoubtedly, becoming infected with HIV will have a negative impact on anyone's life, so Stern urges “every gay man with multiple sex partners” bite the bullet and take Truvada.

With news of Knox's “definitively documented” proof that an HIV infection can occur even “in the context of consistent adherence to PrEP,” further discussion will undoubtedly grow heated. Yes, PrEP is imperfect, but scientists never claimed it was anything but. The question for anyone has never been whether Truvada is infallible or not, but whether it is beneficial. For most people at high risk of HIV, this news does not change that key question — or, for that matter, the answer.

Source: Knox DC, Tan DH, Harrigan PR, Anderson PL. HIV-1 Infection With Multiclass Resistance Despite Preexposure Prophylaxis (PrEP). Conference on Retroviruses and Opportunistic Infections. 2016.