Essential criteria for evaluation of pneumococcal conjugate vaccine candidates

In 2003, the World Health Organization recommended a concentration of enzyme-linked immunosorbent assay (ELISA) immunoglobulin G (IgG) anti-capsular antibody of 0.35 μg/mL as a reference value that correlates to protection against invasive pneumococcal disease. This threshold can be used to demonstrate immunologic non-inferiority of a new vaccine in comparison trials that use pneumococcal conjugate vaccines (PCVs) as a comparator. An investigational 13-valent PCV (PCV13) compared with seven-valent PCV (PCV7) demonstrated that all of the pneumococcal serotypes contained in PCV13 were immunogenic, with 88–98% of vaccinees achieving antibody concentration ≥0.35 μg/mL for serotypes shared with PCV7 and >96% for six additional serotypes.