Final Model Dynamics

When running our model on the whole United States population aged 20-49, we can clearly see that in the disease free steady state after 20 years we need 500,000 people to be on PrEP. This means that when HIV is eradicated, 500,000 people will have been put on PrEP. This is also what is needed to get the effective control reproduction number below 1, which reinforces that HIV is no longer an epidemic. This is equivalent to a .3% (.003) update rate of people on PrEP. These numbers all paint the picture of how PrEP helps HIV become a disease that can become eradicated. 

Number of HIV Cases Prevented by PrEP


While the model dynamics display the way PrEP impacts the HIV system dynamics, we seek to determine the exact impact of PrEP on eliminating HIV. When analyzing system dynamics in the presence and absence of PrEP, we found that PrEP prevents minimal cases of HIV. This can be seen in the figure above, and when all of these values are summed, it can be shown that PrEP saves 87 cases of HIV in the United States. This low number can be explained by the fact that ART is already highly effective and driving the infected population down to zero even without PrEP. Therefore, while the addition of PrEP is important in its preventative sense, it does not prevent a large amount of cases. Further, when running cost effective analysis, PrEP is not all that cost effective since there are not enough cases being saved to justify the high costs. However, it should still be noted that each person put on PrEP is someone who will not contract HIV nor have to experience the burden this disease adds on one’s life experience.