OBJECTIVES: This study aimed to evaluate the potential public health impact of switching from PCV13 to PCV15 in the national immunization program (NIP) for infants in Chile.

METHODS: A state-transition Markov model was used to simulate the occurrence of cases and deaths associated with pneumococcal disease (PD) in the Chilean population. The model incorporated three health states: no PD, post-meningitis sequelae (PMS), and death; and tracked the occurrence of acute PD events, including acute otitis media (AOM), non-bacteremic pneumococcal pneumonia (NBPP), and invasive pneumococcal disease (IPD). Health outcomes, including life-years (LYs) and quality-adjusted life-years (QALYs) were reported. The initial birth cohort in 2024, consisting of 335,715 newborns, and the subsequent 100 cohorts were eligible to receive either PCV13 or PCV15 according to the 2+1 schedule (2, 4, and 12 months). Chilean-specific data from official sources/literature were used, with data from other Latin America countries as proxy, when unavailable. The same vaccine-type efficacy and waning profile was assumed for both vaccines. For the two additional PCV15 serotypes (22F and 33F), the average overall PCV13 vaccine efficacy was applied, including indirect effect for the first five years following the introduction of PCV15.

RESULTS: Switching from PCV13 to PCV15 in the Chilean NIP was projected to prevent additional 4,953 IPD cases, 21,339 NBPP cases, 736,547 AOM cases and 52 PMS cases over a 100-year time horizon. Additionally, PCV15 was estimated to prevent 451 IPD deaths and 29 pneumonia deaths compared to PCV13, leading to gains of 11,051 LYs and 11,034 QALYs over the 100-year time horizon.

CONCLUSIONS: Switching from PCV13 to PCV15 is projected to significantly reduce the cases and deaths associated with pneumococcal diseases in Chile. The results highlight the positive public health impact of PCV15 in preventing PD mortality and morbidity in Chile for both vaccinated and unvaccinated cohorts.