While both genotypes immunised with Pneumovax were protected in the challenge infection (Fig. 1b), localising pneumococci to alveolar macrophages (Fig. 1c), the survival of the non-immunised mice infected in parallel was significantly different (Fig. 1b): while wildtype mice succumbed rapidly, with 2/5 alive at the experimental endpoint of 7 days, 4/5 properdin-deficient mice remained alive. Here, CFP is linked to infection.