A dueling study-and-commentary combination in a recent issue of Clinical Infectious Diseases raises conflict-of-interest concerns amidst a conversation regarding the results of efforts to scale up PrEP access in the U.S.
The study compared state-level data on annual HIV diagnoses and PrEP prescriptions from a single pharmacy database over a four-year period (2012-2016). It concluded that the estimated annual percentage change in diagnosis rates dropped by 4% in the 10 states with the greatest increase in PrEP coverage.
The authors conceded that this is an association, not a causal relationship. Nonetheless, they called for scaling up PrEP to everyone at high risk for seroconversion, contending that the data indicated a population-level benefit of doing so.
While the accompanying commentary agreed with the need for further scale-up of PrEP availability and lamented its slow uptake, it called into question the extent to which the study findings should be used to link greater PrEP access to a reduction in HIV diagnoses, and to make policy decisions based on that suggestion.
The comment authors—Julia Marcus, Ph.D., M.P.H., of Harvard Medical School; A. David Paltiel, Ph.D., of Yale School of Public Health; and Rochelle Walensky, M.D., M.P.H., of Massachusetts General Hospital—questioned the choice of data points on which the study chose to focus, noting that a PrEP prescription does not mean the patient is actually taking the medication, and that HIV diagnosis rates are not incidence rates. They also noted that the prescription data excluded large pharmacy networks, such as Kaiser Permanente.
Marcus et al. added that greater PrEP rollout may also increase the frequency of HIV testing or linkage to care, which could affect diagnosis rates independent of the prevention medication. In the era of U=U, viral suppression rates could further influence the effect of biomedical prevention: With everyone virally suppressed, PrEP would make little difference in seroconversion rates.
Some unavoidable context to the tension between the study and the commentary lies within their respective conflict of interest statements: Two of the 10 study authors are employed by and are shareholders of Gilead Sciences, the maker of both PrEP medications currently on the U.S. market. Meanwhile, one of the three comment authors disclosed a consulting relationship with Kaiser Permanente and the receipt of a Gilead research grant.
Ultimately, the commentary authors concluded their critique with a call for further population-level studies on PrEP’s impact. “In the meantime, while PrEP remains an essential component of our HIV prevention strategy, the jury is still out on its population-level impact,” they wrote.