Impact of 23-valent pneumococcal polysaccharide vaccination on non-invasive pneumococcal pneumonia: A regression discontinuity analysis.

The aim of this study was to evaluate the impact of the vaccination programme with 23-valent pneumococcal polysaccharide vaccine (PPV23) on non-invasive pneumococcal pneumonia (NIPP) in adults above 60 years old during the first three post-implementation years. For this retrospective impact study with a regression discontinuity design, we included patients aged 56 to 85 years who presented with NIPP at the hospital between November 1, 2016 and September 30, 2023. NIPP was defined as a positive pneumococcal urinary antigen test without meeting criteria for invasive pneumococcal disease (blood and/or cerebrospinal fluid culture positive for Streptococcus pneumoniae). We estimated the overall impact and the impact stratified by time since eligibility for vaccination for each birth cohort. Data were obtained from 14 laboratories throughout the Netherlands, which were estimated to cover 34.9% of the Dutch population. We observed 3821 NIPP patients, of whom 634 were eligible for vaccination. The overall impact was 19.7% (95% confidence interval 8.5, 29.7). Impact estimates decreased over time since eligibility, although non-significantly with overlapping confidence intervals. These insights contribute to the existing body of evidence about PPV23 impact on NIPP, informing future vaccination policy.