Introduction Streptococcus pneumoniae remains a leading cause of invasive pneumococcal disease (IPD), particularly among young children and older adults. Although pneumococcal conjugate and polysaccharide vaccines have reduced IPD caused by vaccine-included serotypes, the emergence of non-vaccine serotypes has increasingly offset these benefits. Updated regional data are essential to inform vaccine strategies in Latin America. Methods We conducted a retrospective, hospital-observational, cross-sectional study of IPD cases diagnosed between 2016 and 2023 at two public hospitals in Chile. Clinical records and laboratory reports were reviewed to collect demographic, clinical, vaccination, and serotype data from patients with confirmed IPD. Descriptive statistics were used to summarize qualitative variables as frequencies and quantitative variables using measures of central tendency and dispersion. Results Non-vaccine Streptococcus pneumoniae serotypes predominated in cases of IPD in children and adults during the study period. In the pediatric population, the most frequently isolated serotypes were 19A, 24F, 6C, and 3, while in adults, serotypes 3, 23A, 23B, 19A, and 6C were identified. Of these, only serotypes 3 and 19A are included in currently available vaccines. Furthermore, vaccination coverage was high in children (75.5%) but very low in adults (6.3%). Mortality was observed exclusively in adults, reaching 20.4%. Discussions IPD in Chile during 2016–2023 was driven mainly by non-vaccine serotypes and was associated with substantial mortality among adults. These findings suggest a replacement of vaccine serotypes by non-vaccine serotypes and reveal critical deficiencies in the protection of adults against serotypes that cause IPD. Updated serotype surveillance and reassessment of pneumococcal vaccine strategies, including adult immunization policies, are warranted to improve prevention of severe pneumococcal disease in Chile and similar settings.
Bravo et al. (2026) studied this question.