Vaccinated Toddler With 15B/15C Serotype Switch Pneumococcal Meningitis.

Streptococcus pneumoniae (S. pneumoniae) remains a leading cause of bacterial pneumonia and meningitis in children globally, despite pneumococcal conjugate vaccine (PCV) implementation. We report a case of fatal pneumococcal meningitis in a fully vaccinated two-year-old male patient. Despite prior PCV13 vaccination, the patient developed meningitis caused by S. pneumoniae serotype 15B in the cerebrospinal fluid (CSF) and 15C in the blood. Genomic sequencing revealed nearly identical isolates differing by a capsular switch mutation. This case highlights the limitations of PCV13 in the context of emerging serotypes like 15B and 15C. The recent approval of PCV20, which includes serotype 15B, offers broader serotype coverage compared to PCV13. Based on these findings, we suggest that further research is warranted to investigate the potential role of PCV20, either as a booster for children under five previously vaccinated with PCV13 or in primary immunization schedules, to enhance protection against the evolving landscape of pneumococcal serotypes and reduce invasive disease. Continued surveillance and adaptive vaccination strategies are crucial, as S. pneumoniae continues to pose a significant threat to young children worldwide.