Comparison of secular trends in pneumococcal serotypes causing invasive disease in Denver, Colorado (1971-2004) and serotype coverage by marketed pneumococcal vaccines

Invasive pneumococcal isolates from three hospitals in Denver, CO, USA were serotyped between 1971 and 2004. Serotype 14 was most common (13.2%), and other prevalent serotypes (3, 4, 6, 9 and 19) together accounted for 44.1% of the isolates. All prevalent serotypes and 91.3% of the total isolates were covered by pneumococcal polysaccharide vaccine, while 79.1% of prevalent serotypes and 56.7% of total isolates were covered by pneumococcal conjugate vaccine. Serotypes 6, 9 and 14 were more common in the final decade than in the first decade studied (37.3% vs. 20.2%), whereas serotypes 3 and 23 were more common in the first decade (18.5% vs. 11.0%).