Propensity of pneumococcal serotypes for invasive disease (meningitis) given carriage, relative to other serotypes or -groups.

The invasiveness index was calculated using all cases of pneumococcal meningitis with serotype or -group information identified during the dry season months of 2007–2009 (N = 113) and pneumococcal carriage (N = 166) identified in Bobo-Dioulasso, Burkina Faso, March 2007– February 2009. Serotyping was based on cerebrospinal fluid polymerase chain reaction testing [8] or Quellung reaction on invasive isolates; and on Quellung reaction for carriage isolates. The table reports serotypes that were found in at least one meningitis case, found in at least three carriers, or included in 10- or 13-valent pneumococcal conjugate vaccines.


Discrimination within the serogroup or between serotypes not possible for some meningitis cases due to PCR algorithm.

PCR serotyping on invasive isolates or CSF cannot discriminate between 12A/B/F, while Quellung typing of carriage isolates identified 12F only.

Cornfield estimation of the confidence interval possible only under certain conditions.