An observational study was undertaken in a cohort of 16 older individuals with chronic lung disorders to measure immunogenicity before and after the first, second, and third immunizations with the 23-valent pneumococcal polysaccharide vaccine. Serotype-specific immunoglobulin G (IgG) and the opsonization index (OI) were measured for serotypes 6B, 14, 19F, and 23F, and unfavourable local and systemic reactions were compared. Serotype-specific IgG and OI levels significantly increased one month following the first, second, and third immunizations. Peak IgG levels were greater after the third vaccination than after the second, although serotypes 6B, 14, and 19F levels were not greater than after the first. When compared to the first and second immunizations, serotype-specific OIs did not differ following the third vaccine. One month after the second immunisation, the level of serotype-specific IgG required to kill 50% of bacteria reduced considerably.

Despite the fact that self-limited local and systemic reactions were more common after the second and third vaccines than after the first, no significant systemic reactions were observed after any vaccine. These findings demonstrate that after the first, second, and third vaccinations, elderly patients with chronic lung illness produce persistent functional serotype-specific IgG, and they support the safety of the second and third vaccines.