Effect of the 13-valent pneumococcal conjugate vaccine on invasive pneumococcal disease in England and Wales 4 years after its introduction: an observational cohort study.

The 13-valent pneumococcal conjugate vaccine (PCV13) protects against key serotypes that increased after routine immunisation with the seven-valent vaccine (PCV7), but its potential for herd protection and serotype replacement is uncertain. The aim of this study was to analyse the effect of the 13-valent pneumococcal conjugate vaccine on invasive pneumococcal disease in England and Wales 4 years after its introduction.