Parker AR, et al. - In order to determine the longevity of the responses to the pneumococcal polysaccharide vaccine (Pneumovax 23, PPV), researchers determined age-specific PPV IgM, IgA, IgG and IgG2 concentrations pre, 4–6 weeks and 6 years post-vaccination in the serum of Prevnar-naïve adults. Outcomes suggest that the age influenced the Pneumovax IgM and IgA but not IgG responses. For all ages, significantly elevated median concentrations 6 years post-vaccination were noted compared to the pre-vaccination titres for PPV IgA, IgG and IgG2 isotypes only. The reference ranges developed were used to assess a cohort of primary immunodeficiency (PID) patients in this study.