Comparison of the immunogenicity and safety of polysaccharide and protein-conjugated pneumococcal vaccines among the elderly aged 80 years or older in Japan: an open-labeled randomized study.

An open-labeled randomized study was conducted to compare the immunogenicity and safety of polysaccharide (PPV23) or protein-conjugated pneumococcal vaccine (PCV7) among the elderly aged 80 years or older. A total of 105 nursing home residents were enrolled in this study. We analyzed the geometric mean concentration (GMC) of serotype-specific immunoglobulin G (IgG) and the geometric mean titer (GMT) of the opsonization index (OI) for serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. The GMCs of serotype-specific IgG and the GMTs of the OI significantly increased one month after vaccination in both groups for all seven serotypes evaluated. In the PCV7 group, study subjects with serotypes 4, 9V, 18C, and 23F exhibited statistically significant elevations in both serotype-specific IgGs and OIs compared to those of the PPV23 group. Both vaccines were tolerated without any severe adverse events, and no differences in systemic adverse events were observed between the two groups, although adverse reactions such as redness and localized swelling were more common in the PCV7 group. Our data demonstrated that the GMCs of serotype-specific IgG and the GMTs of the OI were higher in the PCV7 group compared to those in the PPV23 group. Our study also confirmed the safety of both the PCV7 and PPV23 vaccines in elderly people aged 80 years or older.