Surveillance of pneumococcal serotypes in adults hospitalised with acute lower respiratory tract infection in Bristol, UK.

Introduction: Pneumococcus remains a major cause of adult lower respiratory tract infections (LRTI). Few data exist on the relative contribution of serotypes included in pneumococcal vaccines to community-acquired pneumonia (CAP) and non-pneumonic (NP) LRTI. We measured the burden of all and vaccine-serotype pneumococcal respiratory infection following SARS-CoV-2 emergence to inform evidence-based vaccination policy.
Methods: A prospective cohort study at two Bristol hospitals (UK) including all adults age ≥ 18-years hospitalised with acute lower respiratory tract disease (aLRTD) from Nov2021-Nov2022. LRTI patients were classified as: a) radiographically-confirmed CAP (CAP+/RAD+), b) clinically-diagnosed CAP without radiological confirmation (CAP+/RAD-), or c) NP-LRTI. Pneumococcus was identified by blood culture, BinaxNOW™and serotype-specific urine antigen detection assays (UAD).
Results: Of 12,083 aLRTD admissions, 10,026 had LRTI and 2,445 provided urine: 1,097 CAP + RAD+; 207 CAP + RAD-; and 1,141 NP-LRTI. Median age was 71.1y (IQR57.9-80.2) and Charlson comorbidity index = 4 (IQR2-5); 2.7 % of patients required intensive care, and 4.4 % died within 30-days of hospitalisation. Pneumococcus was detected in 280/2445 (11.5 %) participants. Among adults aged ≥ 65y and 18-64y, 12.9 % (198/1534) and 9.0 % (82/911), respectively, tested pneumococcus positive. We identified pneumococcus in 165/1097 (15.0 %) CAP + RAD+, 23/207 (11.1 %) CAP + RAD-, and 92/1141 (8.1 %) NP-LRTI cases. Of the 280 pneumococcal cases, 102 (36.4 %) were due to serotypes included in PCV13 + 6C, 115 (41.7 %) in PCV15 + 6C, 210 (75.0 %) in PCV20 + 6C/15C and 228 (81.4 %) in PPV23 + 15C. The most frequently identified serotypes were 8 (n = 78; 27.9 % of all pneumococcus), 7F (n = 25; 8.9 %), and 3 (n = 24; 8.6 %).
Discussion: Among adults hospitalised with respiratory infection, pneumococcus is an important pathogen across all subgroups, including CAP+/RAD- and NP-LRTI. Despite 20-years of PPV23 use in adults ≥ 65-years and herd protection due to 17-years of PCV use in infants, vaccine-serotype pneumococcal disease still causes a significant proportion of LRTI adult hospitalizations. Direct adult vaccination with high-valency PCVs may reduce pneumococcal disease burden.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: CH is Principal Investigator of the AvonCAP study which is a collaborative study sponsored by the University of Bristol and funded by Pfizer. CH has previously received support from the NIHR in an Academic Clinical Fellowship. JO is a Co-Investigators on the AvonCAP Study. AF is a member of the Joint Committee on Vaccination and Immunization (JCVI) and, until December 2022 was chair of the World Health Organization European Technical Advisory Group of Experts on Immunization (ETAGE) committee. In addition to receiving research funding from Pfizer as Chief Investigator of this study, he leads another project investigating transmission of respiratory bacteria in families jointly funded by Pfizer and the Gates Foundation. ML, CT, JC, JS, MWP, EB, LJ and BG are employees of Pfizer Inc and may own stock. The other authors have no relevant conflicts of interest to declare.
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