Streptococcus pneumoniae is a major cause of severe disease worldwide, particularly in the elderly population. Due to increasing life expectancy in Japan and elsewhere, an effective vaccine which offers the possibility of prolonged protection is required. Protein conjugated pneumococcal vaccines, which have the ability to boost immunity (immunologic memory) on natural exposure or revaccination, may meet these requirements. An unconjugated 23-valent pneumococcal polysaccharide vaccine (PPSV23) has been available for decades; however data on protection against pneumonia are inconsistent. For the first time, a randomized, modified double-blind trial comparing the 13-valent pneumococcal conjugate vaccine (PCV13) with PPSV23 was conducted in PPSV23-naive adults ≥65 years of age in Japan. This study showed that statistically significantly greater functional antibody responses as measured by opsonophagocytic assays 1 month after vaccination were elicited in the PCV13 group (n = 366) compared with the PPSV23 group (n = 367) for 9 of the 12 serotypes in common with both vaccines and for serotype 6A, unique to PCV13. Local reactions collected within 14 days of vaccination were more frequent in the PCV13 (57.5%, 211/367) than PPSV23 (44.9%, 166/370) group, although severity was generally mild to moderate; systemic and adverse events were similar across groups. There were no treatment-related serious adverse events. Consistent with global studies comparing PCV13 with PPSV23, PCV13 use in Japanese subjects was safe and well-tolerated and elicited greater functional immune responses than PPSV23 for the majority of PCV13-serotypes. PCV13 has the potential to protect against pneumococcal disease in Japanese elderly adults.
Keywords: 13-valent pneumococcal conjugate vaccine; 23-valent pneumococcal polysaccharide vaccine; Japan; elderly; immunogenicity; safety.