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Publication

Nasopharyngeal carriage of **Streptococcus pneumoniae** in Belgian children (2016-2018)

Book - Dissertation

Streptococcus pneumoniae usually resides as a commensal in the human nasopharynx. However, asymptomatic carriage may evolve to pneumococcal disease when this micro-organism migrates from the nasopharynx to other mucosal tissues or sterile sites. The consequence may be a mucosal pneumococcal disease such as acute otitis media (AOM) or invasive pneumococcal diseases (IPDs) such as bacteraemia or meningitis. The primary virulence factor of the pneumococcus is its polysaccharide capsule, which also determines the serotype. More than ninety-five serotypes exist and they vary in their capacity to colonise, to invade, and to activate the host immune system. Currently, a 10-valent (PCV10) and a 13-valent (PCV13) pneumococcal conjugate vaccine are widely implemented in national immunisation programmes to prevent pneumococcal diseases. Belgium implemented PCV13 in its paediatric pneumococcal vaccination programme in 2011, but it was replaced by PCV10 in 2015-2016. With the current research we aimed to gain insight into the impact of the PCV13-to-PCV10 change in Belgium, since concerns had raised regarding the three serotypes that were no longer covered (3, 6A, 19A). The overall objective is to clearly monitor the carriage of Streptococcus pneumoniae in Belgian children between six and thirty months of age. This was accomplished over a three year period, during and immediately after the change in the vaccination programme (2016-2018). We evaluated carriage prevalence, carriage density, serotype distribution, and antimicrobial susceptibility of Streptococcus pneumoniae. Furthermore, risk factors for pneumococcal carriage were evaluated. Children are the major pneumococcal reservoir and source of transmission. Therefore, the studied population included children, either in day-care centres or visiting their physician for AOM as children in these settings are reported to have a high pneumococcal carriage prevalence. A significant increase in the carriage prevalence of serotype 19A was identified in the current research as the PCV10-vaccinated population enlarged. Furthermore, the calculated invasive disease potential for this serotype was high. Additionally, the carriage prevalence of serotype 6C increased, indicating the absence of PCV10-induced cross-protection. These results contributed to policy making, since another change in the vaccination programme was established in July-September 2019; from PCV10 back to PCV13. The current carriage monitoring will be continued, and hence this latest vaccination programme change will be evaluated from its implementation onwards. The obtained results will contribute to the concept of large-scale and long-term carriage monitoring and they will be valuable with an eye towards the introduction of the higher-valent PCV15/20.
Number of pages: 211
Publication year:2020
Keywords:Doctoral thesis
Accessibility:Closed