Serotype distribution of pneumococcal carriage, England and Wales. Serotype distribution of pneumococcal carriage from a longitudinal study carried out by collecting nasopharyngeal swabs every month from 489 individuals including 121 pre-school children (<3 yrs.) for a period of 10 months, from October 2001 to July 2002 in England & Wales [31, 34]. Black bars are serotypes included in PCV7 and white bars are serotypes not included in PCV7. One serotype, 6A, is included in the vaccine serotype group due to evidence of cross-protection.