A Randomized Controlled Clinical Trial of Nasal Immunization with Live Virulence Attenuated Strains Using Human Infection Challenge.

Pneumococcal pneumonia remains a global health problem. Pneumococcal colonization increases local and systemic protective immunity, suggesting that nasal administration of live attenuated (Spn) strains could help prevent infections. We used a controlled human infection model to investigate whether nasopharyngeal colonization with attenuated strains protected against recolonization with wild-type (WT) Spn (SpnWT).