A

Sickle-cell patients are functionally asplenic and at very high risk for invasive pneumococcal disease; studies show that the 23-valent polysaccharide vaccine induces robust antibody responses and sharply reduces invasive infections in this group, whereas it is poorly immunogenic in children <2 y and offers little benefit for recurrent otitis/sinusitis or cystic fibrosis [Ammann et al., 1977, PMID 20575; Bruyn & van Furth, 1991, PMID 1794358].