Changes in pneumococcal nasopharyngeal colonization among children with respiratory tract infections before and after use of the two new extended-valency pneumococcal conjugated vaccines.

AbstractBackground: The 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD–CV) and the 13-valent pneumococcal conjugate vaccine (PCV13) replaced the 7-valent PCV (PCV7) in May 2010 in Korea. We investigated the dynamics of pneumococcal nasopharyngeal (NP) colonization in children with a respiratory illness before and after use of PHiD–CV and PCV13. Methods: From March 2009 to December 2012 NP secretions were obtained from 2176 children aged < 5 years with respiratory diseases. We used the multiplex polymerase chain reaction (PCR) technique to determine pneumococcal serotypes. Results: Among the samples, 468 (21.5%) specimens were positive by multiplex PCR. The overall pneumococcal colonization rate remained stable during the 2009–2012 periods. The serotypes present in PCV7 and serotype 19A decreased in frequency from 36.8% and 26.4% in 2009 to 10.1% and 11.4% in 2012, respectively (χ2 for trend, P < 0.001 and P = 0.007, respectively). The frequency of non-PCV13 se...