Modelling the impact of imperfect HIV vaccines on the evolution of
virulence
Eduardo Massad, Francisco A.B.Coutinho, Marcelo N. Burattini and Claudio J. Struchiner
School of Medicine, University of São Paulo, LIM01/HCFMUSP, SP and FIOCRUZ, R.J.
Brazil
In this very simple model we analyse the impact of imperfect HIV vaccines on the
evolution of HV virulence. The model assumes that the contact function is dependent on
the sexual habits of the involved population and on the replication rate of HIV that infects
the contactant, according to the equatiion
This contact function has the following shape:
We then calculate the reproduction number of HIV for each strain according to the rate of
sexual partner exchange and to a hypothetical vaccine with limited efficacy,
Preliminary calculation are demonstrating that, imperfect vaccine can act as selective
pressure on HIV strain, influencing, therefore, on the evolution of virulence, as shown in
the figure: