Pneumococcal pneumonia in adults – re-emergence of vaccine serotypes: a prospective multicenter cohort study in Germany, 2020–2023

The main burden of non-invasive pneumococcal diseases in adults is largely due to community-acquired pneumonia (CAP). This study aimed to investigate the distribution and dynamics of pneumococcal vaccine serotypes and to determine the proportion of CAP cases attributable to serotypes covered by 13-valent conjugate vaccine (PCV13), the 20-valent conjugate vaccine (PCV20), and the 23-valent polysaccharide vaccine (PPV23) among adults in Germany from 2020 to 2023. In this prospective multicenter cohort study, we analyzed all adult patients with CAP enrolled between January 1, 2020, and December 31, 2023, at 26 centers in Germany who provided urine samples for serotype-specific urine antigen detection (SSUAD) testing. Annual trends of pneumococcal vaccine serotypes from 2020 to 2023 were calculated for all patients and patient groups at risk using cluster-robust generalized linear models with heteroscedasticity-consistent standard errors. Of the 2,028 patients with all-cause CAP, 1,504 (1,008 patients aged ≥ 60 years, 373 younger patients with at least one comorbidity) had urine samples analyzed with SSUAD tests. Overall proportion of vaccine-type pneumococcal pneumonia among all-cause CAP for PCV13, PCV20, and PPV23 serotypes was 5.41% (95% CI 4.12-7.06%), 8.11% (95% CI 6.35-10.31%), and 8.31% (95% CI 6.27-10.93%), and serotype 3 was the most prevalent serotype (52 cases). Among patients aged ≥ 60 years, an increasing annual trend was observed for serotype 3 (OR 1.84, 95% CI 1.01-2.67), PCV13 (OR 1.89, 95% CI 0.89-2.89), PCV20 (OR 1.57, 95% CI 0.99-2.14), and PPV23 serotypes (OR 1.47, 1.04-1.91). The findings demonstrate that vaccine serotypes, particularly serotype 3, continued to circulate and reemerged among older adults with CAP in Germany.