One major health care provider in Northern California (KPNC) boasts sterling success in its sprawling Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis program, with more than 5,000 cumulative years of PrEP use among its members since 2012 and not one new case of HIV among them. But clinicians and researchers at Kaiser Permanente Northern California still aren’t satisfied and are imploring others in the field to broaden their definition of the term “PrEP failure.”
Over the past 18 months, there have been three documented cases of individuals, all men who have sex with men (MSM), contracting HIV while they were adhering well to the daily PrEP regimen according to multiple sources of evidence. (Two of the men contracted rare, drug-resistant strains of the virus that apparently evaded the pair of antiretrovirals in Truvada; the other had an extraordinarily high level of sexual risk taking.)
In a letter to the editor published in Clinical Infectious Diseases, Julia L. Marcus, PhD, MPH, of Harvard Medical School, and various clinicians at Kaiser Permanente argued that “PrEP failures could be defined more broadly as HIV infections that occur at any point along the PrEP continuum of care.” This continuum includes, they wrote, those who test positive for HIV during a consultation for PrEP use, or after seeking out or being referred for PrEP use but not ultimately taking Truvada for prevention, or those who stop taking PrEP.
KPNC’s PrEP program is one of the largest in the nation. For the analysis included in the letter to the editor, the researchers included all those who sought out or were referred for PrEP use at a KPNC clinic between July 2012 (when PrEP was approved) through February 2017.
All told, 7,124 people were screened for PrEP use during this period. Of that group, 26 (0.4 percent) tested positive for HIV during their initial assessment for PrEP use. Of the remaining 7,098 people, 4,991 (70 percent) started taking Truvada for prevention and 2,107 (30 percent) did not. Of those who did not start PrEP, 22 were later diagnosed with HIV, for an infection rate of 1.1 percent per year.
Those who started PrEP took Truvada for a cumulative 5,104 years during the study’s follow-up period, for an average use of 12.4 months. During that time none of them tested positive for HIV.
Of the 1,303 (26 percent) of those who started PrEP who were no longer taking it at the end of the study’s follow-up period, 11 were diagnosed with HIV between their last Truvada refill and the end of follow-up for an HIV infection rate of 1.3 percent per year.
“Strategies are critically needed to ensure that patients start, restart or continue PrEP during periods of risk for HIV acquisition,” the letter’s authors wrote.
To read the abstract of the letter to the editor, click here.