Control of pneumococcal disease by vaccination with capsular polysaccharide has been investigated and promoted with variable enthusiasm for the past 90 years. Despite this the true value of the 23-valent pneumococcal polysaccharide vaccine remains unclear. In particular the ability of this vaccine to provide durable protection in those who require it most is in greatest doubt. With the introduction of the protein-conjugated pneumococcal polysaccharide vaccines new opportunities for prevention exist, but it will be import to rigorously assess their role in at-risk groups to avoid the uncertainty that surrounds the older simple polysaccharide products.