The epidemiology of invasive Streptococcus pneumoniae disease in Croatian children

Background: Invasive pneumococcal disease (IPD) is a major medical problem in childhood. Pneumococcal conjugate vaccines (PCVs) offer a new possibility to reduce the incidence of pneumococcal infections, especially IPD. The aim of this study was to describe the characteristics of IPD among Croatian children and examine the possibilities of introducing different PCVs in our population. Material/Methods: Streptococcus pneumoniae isolates causing IPD during three years (2001, 2005, 2006) in Croatian children younger than 14 years old were collected prospectively. Epidemiological and clinical parameters, results of serotyping, and antimicrobial susceptibility data were evaluated. Results: One hundred strains were collected during the study period. The ages of the patients ranged from 30 days to 13 years (median: 25.5 months). Seventy-nine percent of the isolates were from patients younger than five years old. The incidence of IPD was highest among children younger than two years of age (33.9/100,000). Serotypes 14, 6B, 18C, and 23F accounted for 67% of all serotypes. The overall coverage rates of PCV7, PCV10, and PCV13 were 72%, 80%, and 90%, respectively. Low-level resistance to penicillin was found in 20% of the isolates and high resistance to erythromycin in 33.8%. PCV7 covered 85% of the penicillin-resistant strains and 80% of the erythromycin-resistant strains. Conclusions: The inclusion of a PCV in the immunization program could have a considerable effect on IPD-associated morbidity among Croatian children.