During the 20 years following its licensure, pneumococcal vaccine has not b
een 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 pneumoni
a have been inconclusive. Retrospective studies have convincingly demonstra
ted the effectiveness of vaccination in preventing invasive pneumococcal di
sease, but these findings have only gradually gained acceptance, largely be
cause some observers reject the findings of observational studies or fail t
o 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 pne
umococcal vaccines will become the most important vaccines for adults and c
hildren worldwide.