Relative effectiveness of revaccination with 23-valent pneumococcal polysaccharide vaccine in preventing invasive pneumococcal disease in adult Aboriginal and Torres Strait Islander people, Australia

Background: Aboriginal and Torres Strait Islander (Indigenous) Australians have high rates of invasive pneumococcal disease (IPD), with repeat doses of 23-valent polysaccharide pneumococcal vaccine (PPV23) recommended. We report the relative effectiveness of revaccination using a cohort from linked administrative data. Methods: All resident North Queensland Indigenous adults who received any PPV23 vaccination between 2000 and 2012 were identified and linked with IPD cases. IPD rates were compared for individuals revaccinated >five years after initial PPV23 dose against individuals not revaccinated. Results: Analysed data included 12,809 individuals and 89,612 person-years. Revaccinated adults had similar rates of IPD as non-revaccinated adults, after adjusting for potential confounders (HR = 0.92; 95%CI: 0.35-2.42). Findings were similar for vaccine-specific serotypes (HR = 1.32; 95%CI: 0.32-5.43). Conclusions: Benefits of PPV23 revaccination against IPD in this high-risk population were not demonstrated, although estimates were imprecise. Findings should be validated in other high-risk cohorts, and against all-cause pneumonia as an outcome. Crown Copyright (C) 2019. Published by Elsevier Ltd. All rights reserved.