Association between introduction of 13-valent pneumococcal conjugate vaccine and burden of hospitalized adult pneumococcal disease in Hong Kong – A retrospective database study

There is limited information on the association between burden of pneumococcal disease and vaccination. This study aimed to assess pneumococcal disease burden among adults in Hong Kong by estimating incidence rate (IR), case fatality rate (CFR), healthcare resource utilization and costs before and after the introduction of 13-valent pneumococcal conjugate vaccine (PCV13) into Hong Kong's childhood immunization program (CIP) in 2011. Adults ≥18 years hospitalized with invasive pneumococcal disease (IPD) and pneumonia from 2005 to 2019 were identified from the Clinical Data Analysis and Reporting System (CDARS). Interrupted time series analysis (ITSA) was performed and incidence rate ratio (IRR) was computed to compare baseline and trend of IRs between pre-introduction (2005-2010) and post-introduction (2012-2019) of PCV13. Overall IPD and pneumonia IRs were 0.78 and 5.34 episodes per 100,000 person-years, respectively. ITSA showed no changes in baseline IPD IR (IRR = 0.82; <i>P</i> value = .447) and trend of IR (IRR = 0.98; <i>P</i> value = .112). There was no difference in baseline pneumonia IR (IRR = 0.81; <i>P</i> value = .075), but a marginal (small but statistically significant) reduction in trend was observed in the post-PCV13 period (IRR = 0.98; <i>P</i> value = .019). CFR was 24.12% for IPD and higher at 30.06% for pneumonia. The average total costs per pneumonia episode were higher in the post-PCV13 period (2,975 vs. 2,810 Hong Kong Dollar). IPD and pneumonia incidence fluctuated over the study period. After PCV13 introduction into Hong Kong's CIP, there was only a marginal reduction in trend of pneumonia among adults. CFRs of IPD and pneumonia were high, and disease burden remained substantial.