Introduction: Lower
respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of
pneumonia. Nonetheless, existing
pneumococcal vaccines are less effective against
pneumonia than invasive diseases and serotype replacement is a major concern.
Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung
infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the
vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and
nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or
nanogels, which possess greater immunogenicity than the
antigen alone and are considered safer than approaches based on living cells or
toxoids. These particles can protect the
antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry
powder formulations. They can also increase
antigen uptake, control release of
antigen and trigger innate immune responses.