Trends in serotype distribution and disease severity in adults hospitalised with Streptococcus pneumoniae infection in Bristol and Bath: a retrospective cohort study, 2006-2022

Ongoing surveillance is essential to inform policy decisions and monitor serotype replacement following pneumococcal conjugate vaccination (PCV) deployment. We report serotype and disease severity trends in this retrospective cohort of hospitalised adults in Bristol-Bath, 2006-22. Of 1686 invasive pneumococcal disease (IPD) cases, 1501 (89.0%) had known serotype. We also identified 2033/3719 cases of non-IPD. IPD declined sharply during the early COVID-19 pandemic. Over 2022 it gradually returned to pre-pandemic levels. Disease severity also changed throughout this period: CURB65 severity and inpatient mortality decreased whilst ICU admissions increased. PCV7 and PCV13-serotype IPD decreased from 2006-09 to 2021-22. However, significant residual PCV13-serotype IPD remains, representing 21.7% [15.5-29.6] of 2021-22 cases, highlighting that significant adult PCV-serotype disease still occurs despite 17-years of paediatric PCV usage in the UK. We found increased proportions of serotype 3 and 8 IPD, whilst 19F and 19A re-emerged. In 2020-22, 68.2% IPD cases were potentially covered by PCV20. Article SummaryWe observed significant serotype shifts but perseverance and re-emergence of some serotypes covered by PCVs over this 17-year retrospective study, which found considerable adult pneumococcal disease attributable to PCV-serotypes despite high uptake of paediatric PCV.