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%).