Recent trends in epidemiology of invasive pneumococcal disease in Poland

The objectives of this study were to assess the current incidence of invasive pneumococcal disease (IPD) in Poland (2011-2013), where mass vaccination has not been implemented, and to characterize the Streptococcus pneumoniae isolates responsible for invasive infections by determining their serotype distribution and antimicrobial resistance patterns. For all isolates identification, serotyping and antimicrobial minimal inhibitory concentrations determination were performed based on routine techniques. The highest incidence rates were observed among adults older than 85 years old (4.62/100,000) and children under 1 year of age (4.28/100,000). The general case fatality ratio (CFR) was 25.4%, with the highest CFR in the age group ≥85 years old (59.7%). The most common serotypes were 3, 14, 19A, 4, 9V, 19F, 1, and 23 F (61.3% of all isolates). The 10- and 13-valent pneumococcal conjugated vaccines (PCV) covered 46.0 and 71.8% of all IPD cases, 61.4 and 79.5% of cases in children under two years, and 60.4 and 78.6% of cases involving children under five years of age, respectively. The PCV13 and 23-valent polysaccharide vaccine covered 68.7 and 86.0% of cases in adults >65 years old, respectively. Decreased susceptibility was noted for penicillin (24.8%), cefotaxime (10.0%), meropenem (5.0%), rifampicin (0.8%), chloramphenicol (4.3%), erythromycin (29.7%) and clindamycin (25.6%). Multi-drug resistance characterized 21.6% of the pneumococci tested. Despite deficiencies in the Polish surveillance system and strong underestimation of IPD cases, results of the study showed good theoretical coverage of PCV, which should encourage inclusion of anti-pneumococcal conjugate vaccine into the national immunization program.