Post-13-Valent Pneumococcal Conjugate Vaccine Dynamics in Young Children of Serotypes Included in Candidate Extended-Spectrum Conjugate Vaccines.

After worldwide implementation of 10-valent and 13-valent pneumococcal conjugate vaccines (PCV10/PCV13), a 20-valent PCV (PCV20) was developed. We assessed dynamics of non-PCV13 additional PCV20 serotypes (VT20-13), compared with all other non-VT20 serotypes, in children <2 years of age in late PCV13 (2015-2017) and early PCV (2009-2011) periods. Our prospective population-based multifaceted surveillance included isolates from carriage in healthy children, children requiring chest radiography for lower respiratory tract infections (LRTIs), and children with non-LRTI illness, as well as isolates from acute conjunctivitis, otitis media (OM), and invasive pneumococcal disease (IPD). After PCV13 implementation, VT20-13 increased disproportionally in OM, IPD, and carriage in LRTI. VT20-13/non-VT20 prevalence ratio range was 0.26-1.40. VT20-13 serotypes were more frequently antimicrobial-nonsusceptible than non-VT20 serotypes. The disproportionate increase of VT20-13 in respiratory infections and IPD points to their higher disease potential compared with all other non-VT20 as a group.