Abstract: Group A Streptococcus (GAS) is a ubiquitous bacterial pathogen that exists in many distinct strains, and is a major cause of death and disability globally. Vaccines against GAS are under development, but their effective use will require better understanding of how immunity develops following infection. Evidence from an animal model of skin infection suggests that the generation of enduring strain-specific immunity requires two infections by the same strain within a short time frame. It is not clear if this mechanism of immune development operates in humans, nor how it would contribute to the persistence of GAS in populations and affect vaccine impact. We used a mathematical model of GAS transmission, calibrated to data collected in an Indigenous Australian community, to assess whether this mechanism of immune development is consistent with epidemiological observations, and to explore its implications for the impact of a vaccine. We found that it is plausible that repeat infections are required for the development of immunity in humans, and illustrate the difficulties associated with achieving sustained reductions in disease prevalence with a vaccine.
Chisholm, Rebecca H., Sonenberg, Nikki, Lacey, Jake A., McDonald, Malcolm I., Pandey, Manisha, Davies, Mark R., Tong, Steven Y. C., McVernon, Jodie, Geard, Nicholas, 2020, Epidemiological consequences of enduring strain-specific immunity requiring repeated episodes of infection, Volume:16, Journal Article, viewed 30 November 2023, https://www.nintione.com.au/?p=18214.