Purified pneumococcal polysaccharide type 18C (US Type 56) is manufactured by Pfizer, Inc., for small-quantity distribution by ATCC. The pneumococcal powder type 18C is a component of the current 13-valent vaccine against Streptococcus pneumoniae. The pneumococcal polysaccharide type 18C can be used to assay for type-specific antibodies, research immune responses, and study immunodeficiencies.