The effectiveness of revaccination with pneumococcal polysaccharide vaccine for preventing pneumococcal disease in older adults in England: A population-based cohort study

Background: Pneumococcal disease in older adults in the United Kingdom is rising despite immunisation. A key gap in the literature is the clinical effectiveness of revaccination with the pneumococcal polysaccharide vaccine (PPV23). Methods: A cohort study was performed in England, using electronic medical records in the Clinical Practice Research Datalink. Individuals aged >= 64 years and vaccinated with PPV23 were included. Rates of hospitalised pneumonia (HP) and invasive pneumococcal disease (IPD) were compared between individuals receiving a single PPV23 dose versus those receiving two doses using multi-level Cox proportional hazards models. Propensity score weighting was performed to minimise the effect of confounding covariates across the comparison groups. Results: Between 2006 and 2019, there were 462 505 eligible participants. Of those, 6747 (1.5 %) received revaccination. Two doses compared to one dose was associated with an increased risk of HP (adjusted Hazard Ratio [aHR] 1.95; 95 %CI 1.74-2.20) and IPD (aHR 1.44; 95 %CI 1.41-1.46). In participants aged 64-74 years PPV23 revaccination was associated with more IPD (aHR 2.02; 95 %CI 1.75-2.33) and HP (aHR 1.46; 95 %CI 1.42-1.49). In those aged >= 75 years PPV23 revaccination was associated with more HP (aHR 1.12; 95 %CI 1.08-1.16) with no statistically significant difference detected in risk of IPD (aHR 1.20; 95 %CI 0.94-1.52). Conclusions: No clear benefit of PPV23 revaccination was measured in older adults in this observational study. The small proportion of revaccinated subjects limits the strength of the conclusions. Further research evaluating the clinical effectiveness of PPV23 revaccination is required.