Effectiveness of the 23-valent pneumococcal polysaccharide vaccine against invasive pneumococcal disease among 948,263 individuals ≥65 years of age: A Danish cohort study

This study aimed to estimate the effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPV23) against invasive pneumococcal disease (IPD) among individuals ≥ 65 years of age. We used Danish nationwide databases to obtain information on PPV23 vaccination, covariates and IPD, and linked data on an individual-level using a unique personal identifier. A total of 948,263 individuals were included and followed between June 15, 2020 and September 18, 2021 (58.6% were vaccinated during follow-up). The adjusted vaccine effectiveness was 42% (95% confidence interval (CI): 9%-63%) for all-serotype IPD and 58% (95% CI: 21%-78%) for PPV23-serotype IPD, using no vaccination as the reference.