By Michael Smith, North American Correspondent, MedPage Today
Published: April 16, 2012
Reviewed by Zalman S. Agus, MD; Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner
The pill-a-day approach to HIV prevention can be cost-effective in men who have sex with men, but only in those at high risk for infection, researchers reported.
In a complex mathematical model, so-called pre-exposure prophylaxis, or PrEP, was found to prevent a large number of infections over a 20-year period, according to Jessie Juusola, MS, and colleagues at Stanford University in Palo Alto, Calif.
But the best bang for the buck came when PrEP was aimed mainly at men who have more than five sex partners a year, Juusola and colleagues reported in the April 17 issue of Annals of Internal Medicine.
"Promoting PrEP to all men who have sex with men could be prohibitively expensive," Juusola said in a statement. "Adopting it for men who have sex with men at high risk of acquiring HIV, however, is an investment with good value that does not break the bank."
On the other hand, she noted, regardless of cost-effectiveness PrEP "is still very expensive."
"In the current healthcare climate," she added, "PrEP's costs may become prohibitive, especially given the other competing priorities for HIV resources, such as providing treatment for infected individuals."
The researchers cautioned that their findings vary depending on assumptions about the cost of the pill used – tenofovir/emtricitabine (Truvada) – as well as how attractive men would find PrEP and which men would use it.
Interest in using anti-HIV medications to prevent infection has been growing, after the publication of studies that showed a benefit both in uninfected men who have sex with men and in heterosexual couples in which one partner was infected.
But there has also been criticism of the idea, since a landmark trial showed that treating an infected person reduces the risk of transmission of the virus by about 96%. The argument has been that widespread treatment would work better as prevention than PrEP.
The issue of how cost-effective PrEP would be is also up in the air.
Two previous modeling studies suggested a wide range of costs, the researchers noted, but they did not take into account declining transmission rates over time as more people take PrEP, which would increase cost-effectiveness.
The earlier studies also assumed that PrEP would be a life-long affair, while the current model assumes people would stay on PrEP for 20 years, reducing the cost.
The landmark IPrEx study found that, overall, taking the pill rather than a placebo reduced the risk of infection by 44%, although among those who were highly adherent to the medication, risk reduction was even greater.
But in their model, Juusola and colleagues assumed a risk reduction of 44% and calculated such things as new HIV infections, discounted quality adjusted life-years (QALYs) and costs, and incremental cost-effectiveness ratios in a range of scenarios.
In an untargeted analysis, they found, starting PrEP in all men who have sex with men would prevent 249,156 new infection over 20 years – more than half of what would be expected in the absence of PrEP – at a cost of $480 billion more than current care.
That scenario would see a gain of 2.2 million QALYs, with an incremental cost-effectiveness ratio, compared with no PrEP, of $216,480 per QALY.
On the other hand, if only 20% of men who have sex with men took PrEP, the number of infections prevented and cost would be lower, at 62,759 over 20 years and $95 billion, respectively.
There would be a gain of 550,166 QALYs, with an incremental cost-effectiveness ratio, compared with no PrEP, of $172,091 per QALY.
But targeting just the men who have sex with men considered to be at high risk – those with five or more sex partners a year -- would do considerably better, the researchers found.
In that group, thought to be about 20% of all men who have sex with men, starting PrEP would prevent 167,143 new infections over 20 years, at a total cost of $75 billion over current care. And that scenario would gain 1.4 million QALYs, with an incremental cost-effectiveness ratio of $52,443 per QALY, compared with no PrEP.
But even if only one in five of the high-risk population took the daily pill, it would prevent 41,061 new infections over two decades, cost a net of $14 billion, and gain 352,840 QALYs, with a cost-effectiveness ratio of $40,279 compared with no PrEP, they found.
All the models assume that the current cost of the daily pill – about $26 – but analysis found that cost-effectiveness would be better if the cost dropped below $15 or if the risk reduction was greater than 75%.
The study had support from the National Institute on Drug Abuse, the Department of Veterans Affairs, and the National Institute of Allergy and Infectious Diseases. No conflicts were reported.
Primary source: Annals of Internal Medicine
Source reference:
Juusola JL, et al "The cost-effectiveness of preexposure prophylaxis for HIV prevention in the United States in men who have sex with men" Ann Intern Med 2012; 156.
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