Genomics reveals how competition between bacteria affects the impact of vaccination

A large-scale genetic and modelling study of Streptococcus pneumoniae has provided new insight into how recently-introduced vaccines have eliminated many strains from the species, and the diverse ways in which the remaining bacteria to compete for the chance to replace them. S. pneumoniae is usually found at the beyond the back of the nasal cavity, where it is normally harmless. However, it can move to other bodily sites, resulting in it causing thousands of cases of severe pneumococcal disease each year in the UK, and a far greater disease burden in many low- or middle- income countries. These infections result in pneumonia, bloodstream infections or meningitis, and are most common in young infants and the elderly. In response, two different vaccines have been introduced to combat S. pneumoniae in the UK: the 7-valent vaccine in 2006, replaced by the 13-valent vaccine in 2010. Since children started receiving the vaccine, there has...