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Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission

BACKGROUND: Day care centre (DCC) attendees play a central role in maintaining the circulation of Streptococcus pneumoniae (pneumococcus) in the population. Exposure within families and within DCCs are the main risk factors for colonisation with pneumococcal serotypes in DCC attendees. METHODS: Tran...

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Autores principales: Hoti, Fabian, Erästö, Panu, Leino, Tuija, Auranen, Kari
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2009
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717096/
https://www.ncbi.nlm.nih.gov/pubmed/19558701
http://dx.doi.org/10.1186/1471-2334-9-102
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author Hoti, Fabian
Erästö, Panu
Leino, Tuija
Auranen, Kari
author_facet Hoti, Fabian
Erästö, Panu
Leino, Tuija
Auranen, Kari
author_sort Hoti, Fabian
collection PubMed
description BACKGROUND: Day care centre (DCC) attendees play a central role in maintaining the circulation of Streptococcus pneumoniae (pneumococcus) in the population. Exposure within families and within DCCs are the main risk factors for colonisation with pneumococcal serotypes in DCC attendees. METHODS: Transmission of serotype specific carriage was analysed with a continuous time event history model, based on longitudinal data from day care attendees and their family members. Rates of acquisition, conditional on exposure, were estimated in a Bayesian framework utilising latent processes of carriage. To ensure a correct level of exposure, non-participating day care attendees and their family members were included in the analysis. Posterior predictive simulations were used to quantify transmission patterns within day care cohorts, to estimate the basic reproduction number for pneumococcal carriage in a population of day care cohorts, and to assess the critical vaccine efficacy against carriage to eliminate pneumococcal transmission. RESULTS: The model, validated by posterior predictive sampling, was successful in capturing the strong temporal clustering of pneumococcal serotypes in the day care cohorts. In average 2.7 new outbreaks of pneumococcal carriage initiate in a day care cohort each month. While 39% of outbreaks were of size one, the mean outbreak size was 7.6 individuals and the mean length of an outbreak was 2.8 months. The role of families in creating and maintaining transmission was minimal, as only 10% of acquisitions in day care attendees were from family members. Considering a population of day care cohorts, a child-to-child basic reproduction number was estimated as 1.4 and the critical vaccine efficacy against acquisition of carriage as 0.3. CONCLUSION: Pneumococcal transmission occurs in serotype specific outbreaks of carriage, driven by within-day-care transmission and between-serotype competition. An amplifying effect of the day care cohorts enhances the spread of pneumococcal serotypes within the population. The effect of vaccination, in addition to reducing susceptibility to pneumococcal carriage in the vaccinated, induces a herd effect, thus creating a counter-effect to the amplifying effect of the cohort. Consequently, the critical vaccine efficacy against carriage, required for elimination of transmission, is relatively low. Use of pneumococcal conjugate vaccines is expected to induce a notable herd protection against pneumococcal disease.
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spelling pubmed-27170962009-07-29 Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission Hoti, Fabian Erästö, Panu Leino, Tuija Auranen, Kari BMC Infect Dis Research Article BACKGROUND: Day care centre (DCC) attendees play a central role in maintaining the circulation of Streptococcus pneumoniae (pneumococcus) in the population. Exposure within families and within DCCs are the main risk factors for colonisation with pneumococcal serotypes in DCC attendees. METHODS: Transmission of serotype specific carriage was analysed with a continuous time event history model, based on longitudinal data from day care attendees and their family members. Rates of acquisition, conditional on exposure, were estimated in a Bayesian framework utilising latent processes of carriage. To ensure a correct level of exposure, non-participating day care attendees and their family members were included in the analysis. Posterior predictive simulations were used to quantify transmission patterns within day care cohorts, to estimate the basic reproduction number for pneumococcal carriage in a population of day care cohorts, and to assess the critical vaccine efficacy against carriage to eliminate pneumococcal transmission. RESULTS: The model, validated by posterior predictive sampling, was successful in capturing the strong temporal clustering of pneumococcal serotypes in the day care cohorts. In average 2.7 new outbreaks of pneumococcal carriage initiate in a day care cohort each month. While 39% of outbreaks were of size one, the mean outbreak size was 7.6 individuals and the mean length of an outbreak was 2.8 months. The role of families in creating and maintaining transmission was minimal, as only 10% of acquisitions in day care attendees were from family members. Considering a population of day care cohorts, a child-to-child basic reproduction number was estimated as 1.4 and the critical vaccine efficacy against acquisition of carriage as 0.3. CONCLUSION: Pneumococcal transmission occurs in serotype specific outbreaks of carriage, driven by within-day-care transmission and between-serotype competition. An amplifying effect of the day care cohorts enhances the spread of pneumococcal serotypes within the population. The effect of vaccination, in addition to reducing susceptibility to pneumococcal carriage in the vaccinated, induces a herd effect, thus creating a counter-effect to the amplifying effect of the cohort. Consequently, the critical vaccine efficacy against carriage, required for elimination of transmission, is relatively low. Use of pneumococcal conjugate vaccines is expected to induce a notable herd protection against pneumococcal disease. BioMed Central 2009-06-27 /pmc/articles/PMC2717096/ /pubmed/19558701 http://dx.doi.org/10.1186/1471-2334-9-102 Text en Copyright ©2009 Hoti et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Hoti, Fabian
Erästö, Panu
Leino, Tuija
Auranen, Kari
Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title_full Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title_fullStr Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title_full_unstemmed Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title_short Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland – implications for elimination of transmission
title_sort outbreaks of streptococcus pneumoniae carriage in day care cohorts in finland – implications for elimination of transmission
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717096/
https://www.ncbi.nlm.nih.gov/pubmed/19558701
http://dx.doi.org/10.1186/1471-2334-9-102
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