Revaccination with 23-valent pneumococcal polysaccharide vaccine in the Japanese elderly is well tolerated and elicits immune responses.

BACKGROUND Following primary vaccination of adults ⩾65years of age with 23-valent pneumococcal polysaccharide vaccine (PPSV23), immune responses increase and thereafter appear to decrease over time. With increased life expectancy worldwide, revaccination with PPSV23 may be required for continued protection of the elderly population against pneumococcal disease. The present study evaluated the immunogenicity and safety of revaccination with PPSV23 in the Japanese elderly. METHODS Depending on prior history of PPSV23 vaccination, adults aged ⩾70years were given a first dose (primary group; N=81) or second dose (revaccination group; N=161, at least 5years after first dose) of PPSV23 intramuscularly. Subjects were matched for gender, age, and number and type of comorbidity across both groups. Blood samples were collected before and 4weeks postvaccination to measure serotype-specific immunoglobulin G (IgG) concentrations and opsonophagocytic killing activity (OPA) antibody titers to serotypes included in the vaccine. Injection-site and systemic adverse events (AEs) were collected for 14days postvaccination. RESULTS Baseline serotype-specific IgG geometric mean concentrations (GMCs) and OPA geometric mean titers (GMTs) were generally higher in subjects with a prior history of PPSV23 vaccination than in PPSV23-naïve subjects. The levels of IgG GMCs and OPA GMTs after revaccination were generally comparable to those observed after primary vaccination. Incidences of systemic AEs were comparable between the 2 groups. Although incidences of injection-site AEs were higher following revaccination than primary vaccination, the difference was not clinically significant as most AEs were mild to moderate in intensity and resolved within 5days after revaccination without treatment. CONCLUSION Revaccination with PPSV23 was well tolerated and associated with increases in serotype-specific IgG concentrations and OPA titers in the elderly who received a prior PPSV23 dose at least 5years before. Revaccination with PPSV23 can be safely implemented in the elderly for continued prevention against pneumococcal disease. CLINICAL TRIAL REGISTRY NUMBER NCT02260882.