Stefanie Desmet1, Ine Wouters2, Liesbet Van Heirstraeten3, Philippe Beutels4, Pierre Van Damme2, Surbhi Malhotra-Kumar3, Piet Maes1, Jan Verhaegen1, Willy E Peetermans1, Katrien Lagrou1, Heidi Theeten2. 1. Reference Centre for Pneumococci, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Microbiology, Immunology and Transplantation, KU Leuven, Herestraat 49, 3000 Leuven, Belgium. 2. Centre for the Evaluation of Vaccination, Vaccine and Infectious Disease Institute, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk, Belgium. 3. Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk, Belgium. 4. Centre for Health Economics Research and Modelling Infectious Diseases, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk, Belgium.
Abstract
BACKGROUND: Changes in serotype distribution have been described after the switch from the 13-valent pneumococcal conjugate vaccine (PCV13) to the 10-valent pneumococcal conjugate vaccine (PCV10) in Belgium. AIM: To describe serotype's invasive disease potential and the detailed evolution of serotype distribution and antimicrobial susceptibility of pneumococcal isolates (carriage and IPD) in children up to 30 months of age over a period during and after the vaccine switch (2015-2018). METHODS: S. pneumoniae strains isolated from the nasopharynx of healthy children attending day-care centres (DCCs) and strains from normally sterile sites of children with IPD were serotyped (Quellung-reaction) and antimicrobial susceptibility testing was performed. Invasive disease potential was defined as the serotype-specific odds ratio (OR). RESULTS: The highly invasive (OR > 1) serotypes 12F, 1, 3, 24A/B/F, 33F, 19A, and 9N were not frequently carried (<7.5% of carriage strains). Different serotypes dominated in carriage (23B, 23A, 11A, 15B) versus IPD (12F, 19A, 10A, 33F). PCV13 vaccine serotypes increased in carriage (5.4% (25/463) in period 1 vs 10.3% (69/668) in period 3) and in IPD (7.3% (8/110 in period 1 vs 23.9% (34/142) in period 3) due to an increase (p < 0.01) in serotype 19A. The penicillin non-susceptibility of 19A was lower (p = 0.02) in carriage (6.8%) than in IPD (23.5%). Erythromycin and tetracycline non-susceptibility were more frequent (p < 0.01) in IPD (26.0%; 23.0%) compared to carriage strains (18.2%; 14.5%) and penicillin non-susceptibility increased over the three year study period (carriage: 13.4%, 19.8%, 18.5%, p = 0.05; IPD: 11.8%, 15.0%, 20.4%, p = 0.02). CONCLUSION: Only some of the serotypes with high invasive disease potential (serotype 1, 3, 19A) in Belgium are included in PCV10 and/or PCV13. This reinforces the need for continuous monitoring, both in healthy children as in children with IPD, to better understand the dynamics of pneumococcal disease, to optimise the composition and implementation of PCVs.
BACKGROUND: Changes in serotype distribution have been described after the switch from the 13-valent pneumococcal conjugate vaccine (PCV13) to the 10-valent pneumococcal conjugate vaccine (PCV10) in Belgium. AIM: To describe serotype's invasive disease potential and the detailed evolution of serotype distribution and antimicrobial susceptibility of pneumococcal isolates (carriage and IPD) in children up to 30 months of age over a period during and after the vaccine switch (2015-2018). METHODS:S. pneumoniae strains isolated from the nasopharynx of healthy children attending day-care centres (DCCs) and strains from normally sterile sites of children with IPD were serotyped (Quellung-reaction) and antimicrobial susceptibility testing was performed. Invasive disease potential was defined as the serotype-specific odds ratio (OR). RESULTS: The highly invasive (OR > 1) serotypes 12F, 1, 3, 24A/B/F, 33F, 19A, and 9N were not frequently carried (<7.5% of carriage strains). Different serotypes dominated in carriage (23B, 23A, 11A, 15B) versus IPD (12F, 19A, 10A, 33F). PCV13 vaccine serotypes increased in carriage (5.4% (25/463) in period 1 vs 10.3% (69/668) in period 3) and in IPD (7.3% (8/110 in period 1 vs 23.9% (34/142) in period 3) due to an increase (p < 0.01) in serotype 19A. The penicillin non-susceptibility of 19A was lower (p = 0.02) in carriage (6.8%) than in IPD (23.5%). Erythromycin and tetracycline non-susceptibility were more frequent (p < 0.01) in IPD (26.0%; 23.0%) compared to carriage strains (18.2%; 14.5%) and penicillin non-susceptibility increased over the three year study period (carriage: 13.4%, 19.8%, 18.5%, p = 0.05; IPD: 11.8%, 15.0%, 20.4%, p = 0.02). CONCLUSION: Only some of the serotypes with high invasive disease potential (serotype 1, 3, 19A) in Belgium are included in PCV10 and/or PCV13. This reinforces the need for continuous monitoring, both in healthy children as in children with IPD, to better understand the dynamics of pneumococcal disease, to optimise the composition and implementation of PCVs.