Streptococcus pneumoniae (S. pneumoniae) bacteria, or pneumococcus, can cause many types of illnesses. These range from ear and sinus infections to life-threatening conditions such as pneumonia, bloodstream infections, and meningitis. Pneumococci are surrounded by a polysaccharide capsule, which is thought to help it evade the immune system. Presently, over 90 known serotypes of S. pneumoniae have been identified, of which only a minority produce the majority of pneumococcal infections; a serotype is defined by a unique pneumococcal capsule structure. Currently available vaccines contain antigens made from capsular polysaccharides of 10, 13, or 23 common S. pneumoniae serotypes.

CDC has discovered encapsulated strains of commensal Streptococcus species,S. mitis, S. oralis and S. infantis, that have capsules that are identical to pneumococcal capsules. From this, researchers developed compositions and methods from the species’ biosynthetic capsular genes which show promise for protecting people against pneumococcal disease, either by using these strains as vaccines or probiotics or through development of diagnostic assays. Initial results show cross-protection against eight S. pneumoniae serotypes, including serotype 1, a leading cause of invasive pneumococcal disease globally outside of the US. The capsule components or a modified version of the commensal Streptococcus species could be used to develop a novel live, inactivated or a sub-unit vaccine for S. pneumoniae. Initial concept studies have been performed in animal models.