Pneumococcal serotypes and risk factors in adult community acquired pneumonia 2018–20: a multicentre UK cohort study

Abstract

BackgroundHigher-valency pneumococcal vaccines are anticipated. We aimed to describe serotype distribution and risk factors for vaccine-serotype community-acquired pneumonia (CAP) in the two years pre-SARS-CoV-2 pandemic. MethodsWe conducted a prospective cohort study of adults hospitalised with CAP at three UK sites between 2018 and 2020. Pneumococcal serotypes were identified using a 24-valent urinary-antigen assay and blood cultures. Risk factors associated with vaccine-type pneumonia caused by serotypes in the 13-, 15- and 20-valent pneumococcal conjugate vaccines (PCV13, PCV15, PCV20) and 23-valent pneumococcal polysaccharide vaccine (PPV23) were determined from multivariable analysis. FindingsOf 1921 adults hospitalised with CAP, 781 (40·7%, 95% confidence intervals (CI) 38·5-42·9%) had pneumococcal pneumonia. A single PCV13-serotype was detected in 242 (31·0%, 95% CI 27·8-34·3%) pneumococcal CAP patients, mostly serotype 3 (171/242, 70·7%, 95% CI 64·5-76·0%). The additional two PCV15-serotypes were detected in 31 patients (4%, 95% CI 2·8-5·6%), and PCV20-non13-serotypes in 192 (24·6%), with serotype 8 most prevalent (123/192, 64·1%, 95% CI 57·1-70·5%). Compared to PCV13-serotype CAP, people with PCV20-non13 CAP were younger (median age 62 versus 72 years, p<0·001) and less likely to be male (44% versus 61%, p=0·01). PPV23-non13-serotypes were found in 252 (32·3%, 95% CI 29·1-35·6%) pneumococcal CAP patients. InterpretationDespite mature infant pneumococcal programmes, the burden of PCV13-serotype pneumonia remains high in older adults, mainly due to serotype 3. PCV20-non13-serotype pneumonia is more likely in younger people with fewer pneumococcal risk factors. FundingUnrestricted investigator-initiated research grant from Pfizer; support from National Institute for Health Research (NIHR) Biomedical Research Centre, Nottingham.