HIV Prevention Pill’s Value Varies by Target

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.”

How can HIV transmission be prevented?

HIV can be transmitted in three main ways:

- Sexual transmission
- Transmission through blood
- Mother-to-child transmission

For each route of transmission there are things that an individual can do to reduce or eliminate risk. There are also interventions that have been proven to work at the community, local and national level.

Wherever there is HIV, all three routes of transmission will take place. However the number of infections resulting from each route will vary greatly between countries and population groups. The share of resources allocated to each area should reflect the nature of the local epidemic - for example, if most infections occur among men who have sex with men then this group should be a primary target for prevention efforts.

“Knowing your epidemic in a particular region or country is the first, essential step in identifying, selecting and funding the most appropriate and effective HIV prevention measures for that country or region.” UNAIDS guidelines for HIV prevention.

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.

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