Invasive pneumococcal disease in Latin America: serotype distribution and vaccine coverage among adults in Mexico,...

Invasive pneumococcal disease (IPD) causes substantial morbidity and mortality among adults in Latin America. Despite high pediatric pneumococcal conjugate vaccine (PCV), uptake, adult coverage remains low, and residual IPD burden persists. Among currently available PCVs, PCV21 and PCV20 are the newest higher-valency formulations. PCV21 includes eight unique serotypes to address residual adult disease. This analysis quantified the proportion of IPD cases in Argentina, Brazil, and Mexico attributable to PCV21 serotypes compared with those in other pneumococcal vaccines to estimate potential disease coverage.

We conducted a cross-sectional analysis of SIREVA II surveillance data from Argentina and Mexico (2016-2023) and Brazil (2016-2024). Adults aged 50-59 years and ≥ 60 years with laboratory-confirmed IPD and available serotype data were included. We summarized serotype distributions and estimated the proportion of IPD attributable to PCV21 and other recommended vaccines by country, age group, and year. Secondary analyses compared PCV21-unique with PCV20-unique serotypes.

A total of 5012 IPD cases were identified, with a higher burden among adults ≥60 years and a marked decline during 2020-2021 followed by a rebound. Serotype 3 predominated across countries, with additional contributions from serotypes 8, 19A, and 12F. Higher-valency vaccines consistently showed greater coverage. In adults aged 50-59 years, coverage ranged from 7-15% for PCV10, 37-42% for PCV13, 41-44% for PCV15, 59-63% for PCV20, 61-70% for PPSV23, and 67-72% for PCV21. In those aged ≥60 years, coverage ranged from 1-11%, 1-15%, 26-46%, 46-61%, 49-67%, and 55-69%, respectively. PCV21-unique serotypes accounted for approximately 19-26% of disease and consistently exceeded PCV20-unique serotypes.

PCV21 offers substantially broader potential coverage for adult IPD than PCV20 and earlier-generation PCVs in Argentina, Brazil, and Mexico. If incorporated into adult immunization programs with sufficient uptake, PCV21 could meaningfully reduce IPD burden.