Figure 2.

Streptococcus pneumoniae serotype distribution by age group among children hospitalized with invasive pneumococcal disease prior to the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) (1997–2000), during a period of increasing PCV7 coverage (2001–2004), in the late PCV7 period (2005–2010) when vaccine coverage exceeded 80%, and in the early 13-valent pneumococcal conjugate vaccine (PCV13) period (2011–2014). The area of the squares represents the number of cases attributable to each serotype.