(289) Serotype Distribution, Antibiotics Use, and Antimicrobial Resistance in Paediatric Patients with Pneumococcal Infection in Hong Kong – a Population-based Study

Background: Streptococcus pneumoniae, with the variation in serotype, is the aetiology for pneumococcal disease (PD). The effective treatment of PD is hindered by antimicrobial resistance (AMR). Preliminary findings suggested the paediatric patients are at increased odds of having AMR PD infection.

Objectives: To describe the epidemiology and serotype distribution among paediatric PD episodes from 2004-2021. Moreover, to compare the disease incidence, antibiotics use, and AMR status before and after the introduction of various valences of pneumococcal conjugate vaccine (PCV) in Hong Kong (HK).

Methods: We retrieved data from the Hong Kong Clinical Data Analysis and Reporting System. PD-related hospitalisations were identified by diagnostic codes in the International Classification of Diseases, Ninth Revision, Clinical Modification. Antimicrobial susceptibility tests (AST) and serotyping results were retrieved to describe the AMR status and epidemiology. We further grouped the episodes into respective birth cohorts according to the valency of PCV recommended in HK’s immunisation programmes at their birth, i.e. pre-PCV (children born 01/2004-08/2009), PCV7 (09/2009 – 07/2010), PCV10 (08/2010 – 11/2011), PCV13 (12/2011 – 12/2021). Episode-level antibiotic use was aggregated as days of therapy (DOT) and the number of antibiotic classes prescribed according to the British National Formulary (BNF).

Results: Out of 1,391 episodes identified from 1,354 patients within the study period, about half of the episodes (53%, n = 742) were from the pre-PCV cohort, while about one-third (30%) of the episodes were from the PCV13 cohort. The overall incidence of PD was the highest in 2016. At the age of 2, the highest incidence of PD was observed across different PCV generations. Of all episodes, 796 episodes (57%) had AST results reported, of which 37% (n = 294 of 796) were non-susceptible to ≥3 classes of antibiotics, and 34% (n = 273 of 796) were non-susceptible to 2 classes of antibiotics. 97 episodes (6.9%) had serotype information. A growing proportion of serotype 3 PD infections was observed since the introduction of PCV13 in 2011 and contributed to 42% (n = 42 of 97) of all PD episodes with serotype information. Antibiotic use was steady across various birth cohorts.

Conclusions: Increased circulation of serotype 3 emerged since the introduction of PCV13. It was suspected to threaten the community through the transmission to adolescents born before PCV7. More investigations would be deemed necessary to identify the indirect protection and waning of immunity of PCV-vaccinated birth cohorts.