New safety information for an old vaccine.

The pneumococcus continues to be a major killer despite advances in medical treatment. The pneumococcus' polysaccharide capsule is its main weapon. The pneu-mococcus has 90 distinct versions (i.e., seroptypes) of polysaccharide capsule that help the organism to avoid capture by the immune system. For approximately a century , researchers have been developing pneumococcal vaccines that are based on the polysaccharide capsule. A version targeting 6 capsular serotypes (the 6-valent vaccine) was used briefly during World War II. A 14-valent version was licensed in 1977 and was followed by a 23-valent formulation in 1983. The 23-valent version is currently in use, although, since 2003, only a single manufacturer has produced the vaccine (Pneumovax 23; Merck). The 23-valent vaccine is used in many countries for older adults and for persons aged у2 years with chronic illnesses that put them at a higher risk for pneumococcal disease, compared with healthy persons. Studies suggest that the 23-valent vaccine is effective against invasive pneumococcal disease (including bacteremia, pneumonia with bacteremia, and meningitis) but may not be effective against pneumonia without bacteremia [1]. Adults become increasingly at risk for invasive pneumococcal disease as they age, so, ideally, a pneumococcal vaccine should be used in a way that will provide protection over decades. Current US recommendations for pneumococcal poly-saccharide vaccine use in the general population suggest that the vaccine should be given to all adults starting at age 65 [2]. Revaccination is not routinely recommended ; immunocompromised persons or older persons vaccinated before age 65 should receive a second dose if at least 5 years have passed since receipt of the first dose. The recommendations of the Advisory Committee on Immunization Practices were last published in 1997, and the committee is now considering revisions. Some opinion leaders have advocated that the vaccine be given to all adults starting at age 50, when many people start to develop medical conditions that place them at a higher risk for pneumococcal disease and when patients start to receive other preventive health measures [3]. Although we have decades of experience with the pneumococcal polysaccharide vaccine, a few questions remain about its safety and performance, and these gaps in knowledge become evident when thinking about vaccinating all adults at a younger age than is currently recommended. One problem with starting vaccination for all adults at age 50 is deciding when and how often to revaccinate to provide protection as people age and …