Once upon a time, long, long ago, high upon a hill in Montreal, I worked in a lab where I grew cells infected with HIV and spent a lot of time pipetting genetic material onto trays. Once upon a time I knew a lot about immunology, specifically, the immunology of HIV progression. Now I feel like I know next to nothing on the subject.

Last week, the annual CROI conference was held in Montreal. I have been getting updates here and there on some of the key papers presented at this conference and a few of them caught my eye, largely due to the policy implications of these studies. I will try to post on a few of these in the coming week.

The first report is based on the findings of two large cohort studies from Africa which suggests that the current treatment guidelines for ARVs are probably insufficient to make dramatic changes in mortality. The basic story goes something like this: HIV kills off your immune system, ARV allows your immune system cells to return, however, there appears to be some sort of damage that gets done when you have CD4 cells below a certain level for a certain amount of time. What ever the mechanism it means that when you treat people at low levels of CD4 levels they may not really lower their mortality rates as would be hoped. In developed countries, people generally start ARV treatments much earlier than they do in resources constrained environments.

So what does this all mean for the global HIV/AIDS response? First, it probably means that we have overestimated the impact of the rollout of ARV treatment programs and that resources could be more effective (potentially more cost-effective?) if they were directed at treating people earlier into their disease. Whether this is doable ethically, or in the context of countries with low testing rates (people generally present quite late) and lots of stigma and fear of the disease remains to be seen, but a shift in thinking of treating not just those who are most sick but also those who might benefit the most from treatment might have a larger impact in the long-run.

Second, it probably also means that we have greatly underestimated the costs of scaling up treatment programs in developing countries. I don’t know what the distribution of CD4 count levels in HIV infected individuals but would expect that the 350 cut point is much closer to whatever peak density there is in the distribution, meaning that a shift from 250 to 350 CD4 cells could mean a whole heck of a lot more people and hence cost a whole heck of a lot more money.

So more money and less impact that was estimated. Not a good combination.

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