Two years have passed since the CDC issued guidelines stating that thousands of people (particularly those at high risk) start taking pre-exposure prophylaxis (PrEP) to prevent HIV infection. PrEP has been shown to be 99 percent effective at preventing HIV transmission among those who take it as prescribed. The CDC also reports that PrEP has the potential to reduce HIV infections in the US by 70 percent. Nearly 2,500 people in the US are reported to be using PrEP and numbers are slowly rising.
But last week, researchers reported the first documented case of a man who contracted HIV while using PrEP regularly. His pharmacy records showed consistent pharmacy refills and a blood test confirmed he had been taking the drugs. The man is believed to have been taking the treatment for two years when he contracted a multi-drug resistant strain of HIV. New research data from the CDC suggests that about 2 in 10 individuals infected with HIV in recent years involved strains of the virus harboring mutations conferring at least partial resistance to one ore more available antiretroviral (ARV). In this case, the strain of infection was found to be resistant to emtricitabine and tenofovir, which are the two main ingredients of PrEP.
Because the strain had a variation of resistance mutations, it is believed that this particular strain is resistant to the majority of HIV medications.
Despite the level of resistance, it is reported that the man is currently on successful HIV treatment. His story and identity were kept secret until doctors could analyze what exactly happened in his case.
David C. Knox, MD, an HIV specialist at the Maple Leaf Medical Clinic in Toronto, presented data on the patient at the Conference on Retroviruses and Opportunistic Infections for the first time. Dr. Knox told attendees, “to our knowledge, this is the first reported case of breakthrough HIV infection with evidence of long-term adherence to [PrEP].” The highly resistant strain has many researchers and users of PrEP wanting to find answers.
The man in question could undergo more tests, but further analysis seems unwarranted after the catalogue of tests the man has already undergone. Moreover, if PrEP is 99 percent effective, he could indeed be that 1 percent. While none of the nearly 10,000 people in the famed iPrEx study of PrEP among gay and bi men and trans women acquired HIV — and mutation like this wasn’t seen among the participants — scientists have always argued there could be a very small possibility of such. Highly resistant strains of HIV are rare, but they do happen.
While resistance to tenofovir is cited as a main concern among people living with HIV who are resistant to treatment worldwide, tenofovir-resistant strains of HIV only account for about 1 percent of all cases. Resistance to PrEP’s other active ingredient, emtricitabine, is more common, but the strain that managed to bypass the safety of PrEP and infect the man in this study involved a mutation that was resistant to both medications, which is extremely rare. While this case proves that there is no 100 percent guarantee when using PrEP, most experts say that PrEP is still highly effective in preventing the contraction of AIDS.
