Vaccination by delayed treatment of infection.

Two medical interventions allow us to combat infectious diseases: vaccination which can be administered well in advance of exposure, and antimicrobials which are most often administered contemporaneously with exposure. In this paper we show how they can, in principle, be combined - with infection followed by treatment being used as a form of vaccination. We use mathematical models to examine how appropriately administered antimicrobial treatment following natural infection can be used to reduce the pathology caused by the infection, and also generate long-lasting immunological memory to the pathogen. The models explore the tradeoff between reduction in pathology and strength of immunization. This tradeoff suggests a limited treatment window during which antimicrobial treatment can be started and provide both amelioration of disease symptoms and long-term immunity. This approach may be particularly well suited to combat the emergence of novel pandemic influenza infections particularly for individuals such as medical healthcare professionals at greatest risk for exposure during the initial stages of a pandemic.