Increase in Serotype 6C Pneumococcal Carriage, United Kingdom

To the Editor: Streptococcus pneumoniae is a major human pathogen. In 2007, Park et al. identifi ed a novel serotype, 6C (1), which emerged from serotype 6A. A study of children in the Netherlands who had not previously received a pneumococcal vaccine found low prevalence of this newly identifi ed serotype before the heptavalent pneumococcal conjugate vaccine Prevnar/Prevenar (PCV7) (Wyeth, Taplow, UK) was introduced (2). Studies have shown cross-protection between vaccine serotype 6B and vaccine-related serotype 6A. However, PCV7 elicits no cross-protection against serotype 6C.