Childhood invasive pneumococcal disease caused by non-7-valent pneumococcal vaccine (PCV7) serotypes under partial immunization in Taiwan

Background/Purpose: Emerging non-7-valent pneumococcal conjugate vaccine (PCV7) serotypes have replaced PCV7 serotypes in childhood invasive pneumococcal disease (IPD). This study was designed to describe the IPD caused by non-PCV7 serotypes under partial PCV7 immunization in Taiwan. Methods: All children <18 years of age diagnosed with IPD at National Cheng Kung University Hospital from 1998 to 2010 were enrolled. Clinical and laboratory information was collected. Pneumococcal isolates were tested for antimicrobial susceptibility and interpreted using Clinical Laboratory Standard Institute guidelines (2008). Serotypes were determined using the capsular swelling method. Results: One hundred and five patients with IPD were identified, including 75 PCV7 and 30 non-PCV7 isolates. Pneumonia (63.3%) was the leading clinical manifestation of non-PCV7 IPDsand 78.9% of pneumonia cases were associated with necrotizing pneumonia or empyema. Children with non-PCV7 IPDs had longer febrile days, required longer intensive care unit stays,and had a higher C-reactive protein level than those with PCV7 IPDs ( p<0.05). Serotype3 is the most common non-PCV7 serotype (46.7%) and possesses the highest potentialfor pulmonary complications ( p<0.05, odds ratio: 0.114; 95% confidence interval, 0.013-0.973). Conclusion: The changing epidemiology of IPDs following the introduction of PCV7 has been noted. Expanded serotype coverage of the vaccine is warranted.