Pneumococcal Disease Burden and Pediatric Invasive Pneumococcal Serotype Shifts in Malaysia

<title>Abstract</title> <p> Background <italic>Streptococcus pneumoniae</italic> remains an important cause of invasive and non-invasive bacterial disease. However, nationwide data describing pneumococcal disease burden, antimicrobial susceptibility, and pediatric invasive pneumococcal disease (IPD) serotype shifts in Malaysia remain limited. Methods This retrospective study analyzed culture-confirmed pneumococcal infections reported to the National Surveillance for Antibiotic Resistance (NSAR) database submitted via WHONET from 2017 to 2023 to evaluate disease burden and antimicrobial susceptibility trends. A separate serotype analysis of invasive pneumococcal isolates from children aged \(\:\le\:\)5 collected between 2018 to 2024 was conducted to describe pre- and post-vaccination serotype distribution and monitor the early impact of pneumococcal vaccines (PCVs) in Malaysia. Results A total of 10,237 culture-confirmed cases were identified, with an average incidence of 4.01 per 100,000 population. Incidence varied geographically, with higher rates in Peninsular Malaysia than in Sabah and Sarawak. Children aged ≤ 15 years represented the largest affected group, followed by adults aged \(\:\ge\:\)66 years, with a male predominance. Blood was the most common specimen source, indicating a substantial IPD contribution, although non-invasive specimens collectively accounted for a larger proportion of cases. Antimicrobial susceptibility was preserved for beta-lactams, levofloxacin, linezolid, and vancomycin, whereas resistance was highest to tetracycline, erythromycin, and co-trimoxazole. Among children aged \(\:\le\:\)5 years with IPD, serotype distribution shifted after PCV10 introduction, with declining PCV10 serotype isolates and a proportional increase in serotypes 19A, 3, 19F, and non-vaccine serotypes (NVTs). Conclusion These findings provide baseline evidence to support integrated surveillance of pneumococcal disease burden, antimicrobial resistance, serotype replacement, and PCV impact in Malaysia. </p>