Serotypes of respiratory isolates of Streptococcus pneumoniae compared with the capsular types included in the current pneumococcal vaccine

Abstract

The serotypes of 474 clinically significant Streptococcus pneumoniae respiratory isolates collected during a national surveillance study in 1987-1988 were compared to the capsular types included in the 23-valent pneumococcal polysaccharide vaccine licensed for use in the United States. Overall, 355 isolates (74.9%) belonged to types included in the current vaccine, while another 65 (13.7%) were types serologically related to vaccine types and likely to be protective by virtue of cross-reactivity. Relatively few isolates (9.1%) belonged to nonvaccine serotypes, and only 2.3% were nontypable. The mucoid serotype 3 was most frequent (13.1% of total), followed by 19F (9.3%), 23F (7.4%), 6B and 14 (5.7% each), and 4 and 6A (5.5% each). The most frequent type not included in the vaccine was type 16 (2.1% of all isolates). Thus, nearly 89% of respiratory isolates included in this study were encompassed within the antigenic spectrum of the currently marketed pneumococcal vaccine.