National survey of invasive pneumococcal diseases in Taiwan under partial PCV7 vaccination in 2007: Emergence of serotype 19A with high invasive potential

We conducted an active, population-based laboratory surveillance study to evaluate the epidemiologic features of invasive pneumococcal disease (IPD) in Taiwan. Concurrently, nasopharyngeal colonization of Streptococcus pneumoniae was evaluated among 1128 healthy children aged ≤5 years. The overall incidence was highest among children aged 2-4 years (15.6/100,000). Serotype 19A, which had never been reported in Taiwan previously, caused a substantial fraction of the invasive diseases (OR, 9.6; 95% CI, 3.1-29.4) among children aged 2-4 years. Comparing serotype distributions of the isolates from nasopharyngeal colonization among children aged ≤5 years, serotypes 14 (OR, 17.3; 95% CI, 5.2-57.9) and 19A (OR, 14.9; 95% CI, 1.9-117) had the highest invasive potential. The study found that serotype 19A expanded in Taiwan, a country with a low 7-valent conjugate pneumococcal vaccine coverage. The 7-valent conjugate pneumococcal vaccines covered 73% of cases in children aged between 2 and 4 years, and 64.7% of cases in children aged <2 years. Among patients aged ≥65 years, the 23-valent pneumococcal polysaccharide vaccine covered 70.4% of cases. In the future, a broader pneumococcal vaccine is needed.