Increased nasopharyngeal carriage of serotypes 6A, 6C, and 6D Streptococcus pneumoniae after introduction of childhood pneumococcal vaccination in Hong Kong.

Active surveillance on nasopharygeal carriage of Streptococcus pneumoniae in children was conducted in 5581 children under 16 years old admitted with respiratory illness to the pediatric wards in a Hong Kong teaching hospital during 2008-2010. The isolation rate of S. pneumoniae was 14.5%. The most common serotypes/groups from 911 isolates were 19F, 6B, 23F, 14, 6C, 6A, and 3. Considering only children under 2 years old, the percentage serotype belonging to that of the 7-, 10- and 13-valent conjugate pneumococcal vaccines in S. pneumoniae were 56.0% (115/205), 57% (117/205), and 80.5% (165/205), respectively. The prevalence of penicillin-nonsusceptibility (MIC ≥4.0 μg/mL) was 9.1% and for cefotaxime (MIC ≥2.0 μg/mL) was 14.7%. A high prevalence of non-6B serotype, including 6A, 6C, and 6D was noted after the introduction of PCV7 conjugate pneumococcal vaccines in Hong Kong.