The clinical effectiveness of pneumococcal vaccination: a brief review

Randomized controlled trials have shown that pneumococcal polysaccharide vaccine is efficacious in preventing pneumococcal bacteraemia and pneumococcal pneumonia in young adults. Clinical trials in older adults, however, have been inconclusive, usually because the studies have been too small. Retrospective studies have shown that pneumococcal vaccination is approximately 50-80% effective in preventing invasive pneumococcal disease among older persons. Vaccination in this age group is also very cost-effective. These findings are the basis for the recent expansion of immunisation policies and the growth in vaccine use in many developed countries. Serologic and clinical studies, however, suggest that vaccine-induced protection declines after 3-5 years, leading to widespread concern about the need for routine revaccination. Because pneumococcal polysaccharide vaccine does not induce immunologic memory, the benefits of revaccination can also be expected to be relatively short-lasting. Alternative strategies of immunological priming of adults with pneumococcal conjugate vaccine followed by boosting with polysaccharide vaccine, or perhaps vaccination with one of the newer protein vaccines, should be considered. Because these new generation pneumococcal vaccines could provide a foundation of life-long protection against pneumococcal infection, their widespread use among adults could have an immense impact on public health worldwide.