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Open Access Research article

S. pneumoniae transmission according to inclusion in conjugate vaccines: Bayesian analysis of a longitudinal follow-up in schools

Simon Cauchemez12*, Laura Temime13, Alain-Jacques Valleron124, Emmanuelle Varon5, Guy Thomas124, Didier Guillemot6 and Pierre-Yves Boëlle124

Author Affiliations

1 INSERM U707, Paris, France

2 Université Pierre et Marie Curie, Paris, France

3 CNAM, Paris, France

4 Assistance Publique – Hôpitaux de Paris, Paris, France

5 Centre de Référence du Pneumocoque, Hôpital Européen George Pompidou, Paris, France

6 Institut Pasteur, Paris, France

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BMC Infectious Diseases 2006, 6:14  doi:10.1186/1471-2334-6-14

Published: 30 January 2006

Abstract

Background

Recent trends of pneumococcal colonization in the United States, following the introduction of conjugate vaccination, indicate that non-vaccine serotypes tend to replace vaccine serotypes. The eventual extent of this replacement is however unknown and depends on serotype-specific carriage and transmission characteristics.

Methods

Here, some of these characteristics were estimated for vaccine and non-vaccine serotypes from the follow-up of 4,488 schoolchildren in France in 2000. A Bayesian approach using Markov chain Monte Carlo data augmentation techniques was used for estimation.

Results

Vaccine and non-vaccine serotypes were found to have similar characteristics: the mean duration of carriage was 23 days (95% credible interval (CI): 21, 25 days) for vaccine serotypes and 22 days (95% CI: 20, 24 days) for non-vaccine serotypes; within a school of size 100, the Secondary Attack Rate was 1.1% (95% CI: 1.0%, 1.2%) for both vaccine and non-vaccine serotypes.

Conclusion

This study supports that, in 3–6 years old children, no competitive advantage exists for vaccine serotypes compared to non-vaccine serotypes. This is an argument in favour of important serotype replacement. It would be important to validate the result for infants, who are known to be the main reservoir in maintaining transmission. Overall reduction in pathogenicity should also be taken into account in forecasting the future burden of pneumococcal colonization in vaccinated populations.