Impact of pneumococcal vaccines on invasive pneumococcal disease in Taiwan

In Taiwan, the 23-valent pneumococcal polysaccharide vaccine (PPV23) and the 7-valent pneumococcal conjugate vaccine (PCV7) have been available since January 2001 and October 2005, respectively. A hospital-based surveillance of invasive pneumococcal disease (IPD) in a medical center was conducted from 2000 to 2008 to evaluate the epidemiologic changes after pneumococcal vaccination. A total of 337 episodes in 328 patients were identified. The cumulative coverage rate of PPV23 among persons of age a parts per thousand yen75 years increased from 12% in 2007 to 41% in 2008, and that of PCV7 among children aged < 5 years was 0.7% in 2005 and 25.2% in 2008. The annual incidence of IPD decreased from 6.2 cases per 10,000 hospitalizations in 2000-2005 to 3.8 cases in 2006-2008 (38.5% reduction, P < 0.001), but the fatality rate did not change significantly (24.4% and 21.8%, P = 0.74). The serotype coverage rates of PPV23 and PCV7 were not significantly different between 2000-2005 and 2006-2008 (both P > 0.05). A marked increase of serotype 19A from 2000-2005 (0.5%) to 2006-2008 (11.5%) was found (P < 0.001). In summary, a decline in IPD incidence but not in fatality rate occurred after the availability of PCV7 and the increased usage of PPV23. The rapid emergence of serotype 19A during this period is alarming.