Contributions of capsule, lipoproteins and duration of colonisation towards the protective immunity of prior Streptococcus pneumoniae nasopharyngeal colonisation

► Live attenuated nasopharyngeal S. pneumoniae exposure protects against invasive disease. ► Presence of capsule and lipoproteins during colonisation enhances immunogenicity and protection. ► Colonisation does not induce serum anti-capsular IgG. ► Duration/density of colonisation is important in determining immunogenicity of bacteria. ► Inclusion of capsule may enhance protective immunity of otherwise attenuated strains.