The impact of immunity to a pathogen at the person level is important for influencing host health as well as how pathogens evolve. The impact of immunity at the individual level also plays an important role in mitigating the transmission dynamics of pathogens within host populations in a community.
In the most recent edition of Trends in Immunology, Metcalf et al describe immunity at a population-scale, otherwise known as ‘herd immunity’. The authors outline how individual immunity can be mapped to “population outcomes” and the implications for control of infectious diseases within communities.
Taking measles as an example, the authors describe immunological characteristics that are signatures of herd immunity and represents indirect protection of a population. The authors conclude “that the return on every individual immunized is more than one individual”. This makes immunization one of the most powerful tools in public health.