According to the World Health Organization, 60% of people living with HIV in sub-Saharan Africa are women. Worldwide, the latest estimate is that women account for 50% of all people living with HIV. Clearly, finding ways to prevent sexual transmission of this potentially fatal virus is vital.
Beginning in 2009, Jeanne Marrazzo, an infectious disease specialist at the University of Washington, tried to do just that. Marrazzo and colleagues launched a study that enrolled 5,029 women from South Africa, Uganda and Zimbabwe. The women were assigned to one of three different HIV prevention strategies using so-called pre-exposure prophylaxis, or PrEP. In one study arm, women took the oral anti-HIV drugs tenofovir and emtricitabine. In another arm, it was tenofovir alone. In a third arm, women were given a tenofovir-containing vaginal gel. Some participants received a placebo in the form of a drugless gel or drugless pills.
The study (called VOICE, for Vaginal and Oral Interventions to Control the Epidemic) didn’t work. A total of 312 women became infected with HIV during the trial, and there was no statistically significant difference between women on any of the prophylaxis arms versus the placebo group.
How could that be? PrEP measures prevent transmission of the virus, so how could a fake gel or fake pills be just as effective? The answer, Marrazzo reported recently at the 20th Conference on Retroviruses and Opportunistic Infections, was that the enrollees did not adhere to the prevention measures.
Although the women in the study reported using their assigned PrEP 90% of the time, blood tests revealed that only 30% or fewer of the participants had anti-HIV drug in their bodies at any one time.
The abstract of the paper presented at the conference concluded:
In this population of predominately young unmarried women with high HIV incidence, adherence to study drugs was low, and no study drug significantly reduced risk of HIV acquisition. The VOICE results … suggest that products that are long acting and require minimal daily adherence may be more suitable for this population. Understanding of HIV risk perception and biomedical, social and cultural determinants of adherence in this high-risk population is urgently needed.
The headline to the ScienceNOW report on this study read, “Human Nature Sinks HIV Prevention Trial.” And although the circumstances surrounding this particular trial raise questions about why, exactly, these women might have foregone HIV prevention medication, there is a long tradition of medical non-adherence into which this study falls.
The phenomenon of non-adherence (or the less popular term, noncompliance) seems so obvious at first glance that it must be a non-issue. Of course many people don’t take medicines as they are prescribed. We joke about not following the doctor’s order. That can mean something as common as not completing the entire course of antibiotics. But it also stretches to the more alarming scenario of not following the exact regimen for a take-at-home oral cancer drug. A world of entrepreneurs has galvanized around improving adherence, with such inventions as electronic pillboxes that remind us to take our medicines and bottles that are somehow alert our doctors when they are opened. (Here’s an article on this topic that I wrote for Slate a few years ago. My personal favorite was the drug-filled prosthetic tooth.)
So is it accurate to call it human nature? Maybe, considering that it seems to be a global phenomenon. A 2012 meta-analysis in the American Journal of Medicine looking at adherence to cardiovascular disease prevention measures found that, across all studies (encompassing 376,162 patients), people stuck with their assigned prevention strategy just 57% of the time after a median 24 months. According to that analysis, adherence was unrelated to age of the patient or whether he or she paid for the medication.
Studies examining adherence rates for chronic conditions all reveal the same issue. Secondary adherence (that is, prescription refill) for cardiovascular conditions ranges from about 57% to about 74%. For diabetes, study findings range from 40% to 81%. For respiratory conditions, one study reported secondary adherence to be 7.0% (Stempel et al, 2005, for adherence to the asthma-controlling medications fluticasone and montelukast.) Secondary adherence to drugs for ulcerative colitis appears to be below 40%, and hovering closer to 24%, according to a 2011 study by Kane et al.
The pharmaceutical industry is concerned because non-adherence costs money. A recent report by Capgemini found that worldwide, pharmaceutical companies lose $564 billion annually as a result of us not taking medicines as prescribed. (The report is available online at the in-your-face named website Adherence564.com) In the U.S., that amount is $188 billion. That’s a lot, right? The estimate might be a teensy bit high, considering that the last such calculation, from 2004, put losses at $30 billion annually. The pharmaceutical industry is, in general, extremely profitable. But patients not filling prescriptions results in a loss of revenue for drug makers. Imagine what would happen if we all adhered better to our medication.
As for HIV prevention strategies, clearly any psychological, communication, and social barriers to making good use of these effective approaches need to be broached before headway can be made. Speaking at the Conference on Retroviruses and Opportunistic Infections and as reported by ScienceNOW, Marrazzo said of the study findings, “We think all the time about these grand interventions, and maybe people don’t want to use them from the get-go. We need to start listening to people, and if you’re not going to use this, we’re not going to test this.”