Avidity of antibodies against infecting pneumococcal serotypes increases with age and severity of disease

The incidence of invasive pneumococcal disease (IPD) rises with age. Among adult IPD patients, the avidity of antipneumococcal polysaccharide antibodies against the infecting serotype increased with age and severity of disease, indicating that susceptibility to IPD in the elderly may rather be due to flaws in other aspects of opsonophagocytosis.