The vaccine dosing effect overcomes the reduced immunogenic potential and in vivo efficacy of 33F pneumococcal serotype.

Serotype 33F is an emerging Streptococcus pneumoniae (Spn) serotype associated with asymptomatic nasopharyngeal (NP) colonization and invasive pneumococcal disease (IPD). Serotype 33F is a component in the advanced version of the pneumococcal conjugate vaccine 15 (PCV 15) formulation. However, in the murine vaccination model, serotype 33F exhibits reduced immunogenicity, correlating with reduced protection against 33F.