Vaccines and their impact on the control of disease.

Disease control exerts evolutionary pressures that can lead to the evolution of resistance. This has been seen in a spectacular fashion in the evolution of resistance to antibiotics, anti-virals and anti-parasitics. Despite intense (and often successful) attempts to control infectious diseases through vaccination, there is still rather little evidence of the emergence of strains of pathogen resistant to vaccines. This chapter asks why this should be so and what are the exceptions indicating that the evolution of vaccine resistance, though currently rare, is a possibility that should be planned for.