6. Affordability and cost-effectiveness of the strategy

The affordability of antiretroviral drugs and replacement feeding will depend a great deal on the condition of the health infrastructure within a country or district, and how much strengthening or expansion of services is needed before the strategy can be introduced.

Antiretroviral drugs for mothers known to be HIV-positive and re-placement feeding for their infants are affordable in most countries, or districts within countries, where there are already well-functioning health care systems. For instance, countries that would be able to negotiate a price for the drugs of US$ 50 per woman, and infant formula at US$ 50 for six months, would need to spend US$ 130 per pregnant woman with HIV, including the costs of counselling and other inputs. In countries with a birth rate of 40 per thousand, and 15% HIV prevalence among pregnant women, and assuming that all women who know their status (estimated to be 10%) accept the intervention, the cost per capita of the specific inputs (i.e. drugs and replacement feeds) would amount to US$ 0.08². The much shorter antiretroviral regimens being tested in current trials (PETRA and nevirapine, in Uganda), are likely to be even cheaper than the currently recommended one-month course of ZDV. This calculation does not take into account savings of medical and other expenditures to care for HIV-positive infants - which, though admittedly very low in some countries, can be substantial in others. In fact, the savings may more than compensate for the cost of the intervention.

² Cost per capita = cost per woman × birth rate × prevalence rate of HIV × proportion of women knowing their status: US$ 130 × 0.04 × 0.15 × 0.1 = US$ 0.08 per capita.

Nor does it take into account the wider benefit of the intervention to the general population, which, as has been shown, is often considerable.

Voluntary counselling and testing also needs to be taken into consideration. If the cost of this service is to be borne exclusively by MTCT prevention programmes, the cost-effectiveness of the strategy will depend on the HIV prevalence in the area: the lower the prevalence, the more it will cost to identify each HIV-positive pregnant woman. Models show that cost-effectiveness remains fairly stable at HIV prevalence rates of 5 - 10% and over, but that where the prevalence rate is below this, the cost-effectiveness of the intervention rapidly decreases as the prevalence rate drops. In such situations, targeting HIV screening at women who are pregnant or who plan a pregnancy in specific population groups will lead to greater cost-effectiveness.

Fig 1. Cost-effectiveness by HIV seroprevalence

Where HIV prevalence is high, the cost of a programme of voluntary counselling and testing, antiretroviral drugs and replacement feeding compares well with the cost of interventions for other health problems. It is estimated, for example, that at HIV prevalence rates of more than 5%, this strategy costs around US$ 35 per Disability Adjusted Life Year (DALY), compared with US$ 20-40 per DALY for polio and diphtheria vaccination, and US$ 200-400 per DALY for river blindness prevention.

Definition

Disability-adjusted life-years (DALYs) are the number of years of life gained through a particular intervention, discounted slightly for each successive year gained to take account of the fact that the quality of life diminishes as time passes and the risk of dying of some other disease increases. Thus, the first year of life gained as the consequence of the intervention counts as a full year, whereas each successive year counts for a little less each time. The great strength of DALYs is that they reflect both quality of life and chances of survival, and allow for easy comparison between different kinds of intervention.