Health Strain

New case of PrEP failure documented in San Francisco

Doctors have diagnosed a San Francisco man on PrEP with HIV.

The case marks only the third documented occasion in the United States in which the widely-prescribed and lauded health regimen to prevent HIV infection has failed. The announcement came at IDWeek, a conference for members of the Infectious Diseases Society for America.

Doctors diagnosed the patient with a rare strain of drug-resistant HIV in 2018. He began the PrEP program–a regimen of a daily dose of anti-HIV drug Truvada, along with regular STD and blood testing at 3-month intervals–in 2016. DNA analysis taken from hair samples demonstrated that the man adhered correctly to the program without missing a dose of the drug. Rather, doctors have linked his infection to an HIV+ sexual partner who had stopped taking his own medication.

Related: Man tests positive for HIV while taking PrEP

The patient’s sexual partner carried a rare drug-resistant strain of the HIV virus, and as his viral load began to increase, he passed it along to his partner on PrEP. The levels of Truvada in the PrEP-taking-partner’s body were not high enough to combat the drug-resistant form of the virus. The case marks the fifth documented case of a man on PrEP acquiring HIV despite adhering to the parameters of the regimen.

It’s important to note that despite this new case of PrEP failure, PrEP remains more than 99.9% effective in preventing the transmission of HIV–far more effective than other methods like condoms. Dr. Robert Grant, of the University of California San Francisco, upon hearing of this new case, assured the public that PrEP remains highly effective. “We know PrEP is greater than 99% effective,” he said in a statement. “There are some cases where HIV will break through. We only have a handful of cases now, and next year, we’ll probably have a handful more. Fortunately, these cases are caught early, treated, and suppressed quickly. The person goes from taking one pill a day to one pill a day. The biggest difference is stigma.”

An estimated more than 350,000 people use PrEP worldwide. The drug is widely credited with reducing rates of HIV infection, particularly among gay men. It still remains the most effective method of prevention against HIV.