Pneumococcal vaccination for older adults: the first 20 years.

During the 20 years following its licensure, pneumococcal vaccine has not been widely used. Although the vaccine was shown to be efficacious in South African gold miners, clinical trials of 'pneumonia vaccine' in older adults that have attempted to demonstrate vaccine efficacy in preventing pneumonia have been inconclusive. Retrospective studies have convincingly demonstrated the effectiveness of vaccination in preventing invasive pneumococcal disease, but these findings have only gradually gained acceptance, largely because some observers reject the findings of observational studies or fail to appreciate the importance of invasive disease. In the 1980s, pneumococcal vaccine was used only in the US, but other countries began vaccination in the mid-1990s, in part due to a better understanding of the disease and the vaccine, but also because of concern about antimicrobial resistance. With greater understanding of the global importance of pneumococcal disease and the promise of conjugate and protein vaccines, during the next 20 years pneumococcal vaccines will become the most important vaccines for adults and children worldwide.