Impact of Universal PCV10 Vaccination on Invasive Pneumococcal Disease in Croatian Children

Abstract

Introduction: Despite the worldwide usage of pneumococcal conjugated vaccines (PCVs), Streptococcus pneumoniae remains a major cause of morbidity and mortality among children. This study evaluated the effects of universal PCV10 vaccination on incidence, serodistribution and antimicrobial resistance among S. pneumoniae strains causing invasive pneumococcal disease (IPD) in Croatian children.

Methods: The study analyzed consecutive, nonredundant invasive S. pneumoniae isolates obtained from children up to 18 years of age, collected through a network of microbiologic laboratories in Croatia from 2005 to 2023. Serotyping was performed by the capsular swelling method. In vitro susceptibility testing was performed according to the EUCAST guidelines.

Results: During the 19-year study period, 601 invasive S. pneumoniae strains were analyzed. This included 543 isolates in the pre-PCV10 period and 58 isolates in the post-PCV10 period. Bacteremic pneumonia and serotype 3 were significantly more common in the post-PCV10 period. A significant reduction in the incidence of IPD caused by PCV10 serotypes was observed in the post-PCV10 period in all age groups, with the highest reduction of 81.0% in children <5 years. The cumulative incidence of isolates susceptible, increased exposure to penicillin and isolates resistant to macrolides increased significantly slower in the post-PCV10 period.

Conclusions: The introduction of PCV10 significantly changed the IPD epidemiology in Croatian children. The prevalence of PCV10 isolates decreased, with the current serodistribution suggesting the need for novel pneumococcal conjugates. Given the relatively low prevalence of isolates with PCV10 and PCV13 serotypes, PCV15 and PCV20 may be the most suitable candidates for future use.

Keywords: PCV10 impact; antibiotic resistance; children; invasive pneumococcal disease; serotypes.