Risk of red queen dynamics in pneumococcal vaccine strategy.

Pathogens increasingly evade current vaccines, and new strategies to control them are needed. There is mounting evidence that replacement of vaccine serotypes of Streptococcus pneumoniae with non-vaccine serotypes has taken place following widespread use of limited-serotype conjugate vaccines. New strategies to control vaccine evasion are needed and understanding evolutionary theory is important for the development of such approaches. Hosts are under selection pressure to evolve resistance against pathogens whereas pathogens are under selection pressure to evolve counter-resistance against the resistance mechanism of their host. Evolutionary changes in both host and pathogen lead to a continuous turnover of host and pathogen genotypes; this is known as Red Queen dynamics. We argue that integrating evolutionary thinking into pneumococcal vaccine design will lead to the avoidance of Red Queen dynamics and improved interventions against pneumococci.