Lancet February 2026 Serotype-specific pneumococcal invasiveness: a global meta-analysis of paired estimates of disease incidence and carriage prevalence B

Source guide This meta-analysis explores the invasiveness of various pneumococcal serotypes by comparing how often they live harmlessly in the throat versus how frequently they cause serious illness. By calculating case-carrier ratios across diverse global settings, the researchers identified that a strain's likelihood of causing disease is heavily influenced by patient age, HIV status, and national income levels. Crucially, the study reveals that vaccine introduction has shifted these dynamics differently in wealthy versus low-income countries, highlighting a persistent risk from non-vaccine strains in developing regions. Ultimately, these findings provide a refined mathematical framework for health officials to predict future disease outbreaks using simple carriage data.