Peer-reviewed article
The impact of pneumococcal conjugate vaccines on disease epidemiology, serotype distribution, and antimicrobial resistance in children. A 25-year observational study in Athens, Greece (1996-2021).
Vasiliki P Syriopoulou, George L Daikos, Emmanouil I Koutouzis, Elizabeth-Barbara Tatsi, Theano Georgakopoulou et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This 25-year study tracked how pneumococcal conjugate vaccines (PCV7 and PCV13) changed pneumococcal disease patterns in children aged 14 and under in Athens, Greece. The vaccines significantly reduced invasive pneumococcal disease and eliminated most targeted serotypes, but some non-vaccine serotypes like serotype 3 increased, and antimicrobial resistance rose substantially over the study period. Vaccine failures occurred in about 10% of cases, often involving serotypes not fully covered by the vaccines.
Key points
- Invasive pneumococcal disease declined from 59% in the pre-vaccine period (1996-2005) to 35.1% after PCV13 introduction (2011-2021)
- All PCV7/13 targeted serotypes decreased significantly except serotype 3, which increased and was associated with empyema cases
- Vaccine failures accounted for 9.8% of cases, mostly from serotypes 3, 19A, and 19F
- Multidrug-resistant pneumococcal rates increased from 12.9% to 24.8% over the study period, with serotype 19A becoming the predominant multidrug-resistant phenotype (47.1%) post-PCV13
- Disease burden shifted toward older children over time following vaccine introduction
Limitations
This is an observational study tracking disease trends over time rather than a randomised trial, so causality between vaccines and outcomes cannot be definitively established. The study covers only Athens and may not represent national or international patterns of pneumococcal disease.
Abstract
Streptococcus pneumoniae continues to cause invasive pneumococcal disease (IPD) and non-IPD in children, despite widely implemented pneumococcal conjugate vaccines (PCVs). This study evaluated the impact of PCV7 and PCV13 on pneumococcal disease (PD), serotype distribution, and antimicrobial resistance in children ≤14 years in Athens, Greece. We conducted a retrospective multicenter study in five pediatric hospitals covering ~80% of Athens' pediatric population in three time periods; pre-PCV (1996-2005), post-PCV7 (2006-2010), and post-PCV13 (2011-2021). Clinical, microbiological, and demographic data were collected for children with PD. Capsular typing was performed by the Quellung reaction. Untypeable or antiserum cross-reacting isolates were typed by Next Generation Sequencing (NGS). The minimal inhibitory concentrations (MICs) were determined by Etest. A total of 2546 children with PD were identified and included in the analysis; 1233 (48.4%) with IPD and 1313 (51.6%) with non-IPD. PCVs significantly impacted disease patterns: IPD declined from 59% in the pre-PCV period to 35.1% in post-PCV13, while age distribution shifted toward older children (p < .001). All PCV7/13 serotypes decreased significantly in the post-PCV periods, except serotype 3 which increased, contributing substantially to empyema cases. Vaccine failures were 9.8% of cases, mostly attributed to serotypes 3, 19A, and 19F. Multidrug resistance (MDR) rates rose from 12.9% in pre-PCV to 24.8% in post-PCV13 period (p < .001), with MDR serotypes 19F and 23F decreasing over time and 19A becoming the predominant MDR phenotype (47.1%) in the post-PCV13 era. These findings underscore the dynamic nature of PD in the post-PCV era and highlight the ongoing need for surveillance studies, vaccine updates and resistance monitoring.