The Health and Economic Impact of the Adult-specific 21-valent (aPCV21) Pneumococcal Conjugate Vaccine vs PCV20 on Invasive Pneumococcal Disease Among Adults Aged 65 years in the United Kingdom: A Modeling Study

Introduction: This study compared the health and economic impact of the 21-valent pneumococcal conjugate vaccine (aPCV21) vs the 20-valent pneumococcal conjugate vaccine (PCV20) on invasive pneumococcal disease (IPD) and post-meningitis sequelae (PMS) among adults aged 65 years and older in the United Kingdom (UK). Methods: A published Markov model was used to simulate a single-cohort of vaccine-naive adults who became eligible for age-based vaccination at age 65 years, with uptake occurring over time. The cohort was followed until a maximum age of 100 years. Model inputs were derived from publicly available national health data and published reports. Outcomes were discounted at 3.5% annually, and costs were adjusted to the 2024 Great Britain Pound ({pound}). Additional analyses explored the impact of changing the age-based recommendation from 65 years to 75 years. Scenarios involving instantaneous vaccine uptake rates were included as part of the sensitivity analyses. A deterministic sensitivity analysis was performed on the incremental direct medical costs between vaccinating with aPCV21 vs PCV20 under the age-based recommendation of 65 years. Results: Using an age-based recommendation of 65 years, aPCV21 led to fewer cases, deaths, and costs than PCV20. Compared with PCV20, aPCV21 averted an additional 138 IPD cases, 1 PMS case, and 22 IPD deaths, saving {pound}1.2 million in direct medical costs. Raising the age-based recommendation from 65 to 75 years and using aPCV21 (or PCV20, respectively), resulted in 120 (92) additional IPD cases, 2 (1) additional PMS case(s), 19 (14) additional IPD death(s), and an extra {pound}1.1 ({pound}0.8) million in direct medical costs. The deterministic sensitivity analysis showed that aPCV21 reduced direct medical costs across all parameter ranges. Conclusions: Compared with PCV20, aPCV21 prevented more IPD cases, IPD deaths, and direct medical costs among older adults in the UK. Changing the age-based recommendation from age 65 to 75 resulted in worse health and economic outcomes. Key words. Pneumococcal infections; pneumococcal vaccines; vaccines, conjugate; serotype; United Kingdom; health costs