This hospital-based cross-sectional study aims to determine the prevalence and serotype distribution of nasopharyngeal Streptococcus pneumoniae carriage among children aged 2-59 months hospitalized with acute respiratory symptoms at Vietnam National Children's Hospital (VNCH). Whole genome sequencing (WGS) will be used for serotype identification, antimicrobial resistance gene detection, and characterization of co-colonization patterns. The study will compare carriage prevalence and serotype distribution between previously healthy children and children with underlying comorbidities. Findings will inform pneumococcal vaccine policy and antimicrobial resistance surveillance in Vietnam.