Canada: PrEP use now could save considerable sums in the future

To calculate the cost of PrEP, the researchers added the cost of a year's worth of emtricitabine/tenofovir (Truvada) to indirect costs such as work time missed for clinic visits, clinic staff wages, free condoms and the cost of tests. The cost of Truvada was CA$9505 per year and other costs were CA$2497, or CA$12,001 in total.

The cost of a lifetime's HIV infection was based on diagnosis at age 30 (the average in Quebec) and on the current additional life expectancy (excluding people who inject drugs) of someone diagnosed at that age – 35.2 years. The researchers assume the person with HIV starts antiretroviral therapy (ART) immediately. They cost for two ART regimens, a cheap one (efavirenz/emtricitabine/tenofovir [Atripla]) and an expensive one (boosted darunavir [Prezista] plus [Truvada]). They also assume a 10% a year failure rate for these first two regimens and a second-line regimen of raltegravir or etravirine plus supporting drugs.

The annual drug costs are CA$14,093 or CA$22,040 under the least and most expensive scenario. Hospital costs were actually somewhat less than the annual cost of PrEP care: CA$2016 a year. This is because trial participants in Ipergay were seen every two months whereas the HIV clinic visits are assumed to be quarterly. This leads to a cost per patient, per year, of CA$16,109 for the cheapest drug regimen.

However, the modellers also added in something that is not always added to models of the cost of HIV infection: its cost to the economy in terms of unemployment and loss of productivity. Taking Quebecois estimates of the unemployment rate in people with HIV and the time lost to productivity due to hospitalisations and clinic visits, they calculated that the non-medical cost to the economy of each case of HIV was CA$11,550 per year. The total annual cost to the economy of each person with HIV was therefore CA$27,659 in total for the cheapest drug regimen.

The modellers note that whereas there is clearly a higher unemployment rate among people with HIV in Canada compared with the general population, this is not the case with gay men in general, so they assume typical employment rates for people using PrEP.

Given the expected life expectancy remaining to the average person diagnosed with HIV, this would mean that the cost per lifetime of an HIV infection would be $1,439,984 for the cheapest regimen.

The researchers then used a figure called the 'number needed to treat'. This represents the number of people that would need to be given PrEP to prevent one HIV infection. In iPrEx this number was just under 52, leading to a cost per HIV infection averted of CA$621,390.

This means that PrEP would save CA$818,594 per infection averted.