Models of RNA virus evolution and their roles in vaccine design

Ojosnegros, Samuel; Beerenwinkel, Niko

From the virus dynamics point of view, a successful vaccine is one that boosts the immune response, i.e., increases the parameter a', such that R 0 is reduced below the critical value of 1. Under such conditions, the infection will initially grow, but then viral load will rapidly decline and the infection will eventually be cleared from the organism. However, even if the vaccine induces an immune response that is not strong enough to reduce R 0 to a value below 1, it may still be beneficial. As described above, slowing down the initial exponential increase of the viral load has a negative effect on the viral set point. This type of imperfect vaccine is also called a therapeutic vaccine. In the case of HIV, it could help infected patients to control disease progression in two ways. First, it may reduce viral load during the chronic phase of the infection, and second it may reduce viremia below the threshold of inter-host virus transmission ( Figure 3 ) [137, 144, [155] [156] [157] .