Post-COVID-19 epidemiology of pneumococcal disease in Taiwan: escalating serotype replacement and antimicrobial resistance in all ages

ABSTRSCT Background This study delineated the evolving epidemiology of pneumococcal disease in Taiwan, focusing on emerging serotypes, antimicrobial susceptibility, and genotypes before and after the pandemic. Methods Culture-confirmed pneumococcal disease (CCPD) was analyzed across four Chang Gung Memorial Hospitals in Taiwan in 2019∼2024. Serotypes, multi-locus sequence types, and penicillin and ceftriaxone susceptibility of pneumococcal isolates were determined. Results The incidence of CCPD dropped from 16.09 in 2019 to 5.39 in 2021, followed by a rise to 9.04 in 2024, per 100,000 population. Invasive pneumococcal disease (IPD) accounted for 13.0% (126/969) of CCPD. The most common serotypes for CCPD were 23A (28.4%), 15A (14.2%), 19A (9.5%), and 15B/C (8.7%). Serotype coverage was 24.8% for PCV13, 36.4% for PCV20, and 78.2% for PCV21. Non-PCV13 serotypes contributed to approximately three fourths of CCPD. Penicillin non-susceptibility of non-PCV13 serotypes (59.7%) surpassed that of the PCV13 serotypes (45.7%) in 2024. Penicillin and ceftriaxone non-susceptibility of the isolates from children was higher than that from adults, and such non-susceptibility was more common in isolates from sputum than that from blood. Clonal complex 166 has been emerging as the predominant lineage (27.8%, 269/969), primarily composed of serotypes 23A (85.5%, 230/269) and 11A (6.7%, 18/269). Conclusions The study shows continuously escalating penicillin and ceftriaxone resistance among pneumococcal isolates after the pandemic. Lower β-lactam susceptibility in pediatric upper respiratory tract isolates and adult sputum isolates appear to be derived from the serotype shift for CCPD.