Immunogenicity and safety of 13-valent pneumococcal conjugate vaccine when administered to healthy Japanese adults aged ≥50 years: An open-label trial

This open-label study was designed to assess immunogenicity and safety of 13-valent pneumococcal conjugate vaccine (PCV13) when administered to Japanese adults aged ≥50 years not previously vaccinated with 23-valent pneumococcal polysaccharide vaccine and to compare this Japanese study population with similar study populations in the United States (US; 50–64 years age group) and European Union (EU; ≥65 years age group). Functional antibody immune responses were measured by opsonophagocytic activity assays. Immune responses in both Japanese age groups showed significant pre/postvaccination fold rises for each serotype. In the Japanese 50–64 years age group, immune responses for the majority of serotypes were significantly lower than in the ≥65 years Japanese age group and generally lower than in the 50–64 years age group in the US study. Immune responses in the Japanese ≥65 years age group were significantly higher for the majority of serotypes compared with the ≥65 years age group in the EU study. The safety profiles across age groups and studies were generally similar. In conclusion, PCV13 elicited robust immune responses in the Japanese study population. The unanticipated higher immune responses observed in the older age group in the Japanese study are of interest and of potential benefit given the higher incidence of pneumococcal disease in older adults. PCV13 was well tolerated and safe.