Biomedical subjects

Marie-Pierre Préziosi

Publications and source records attributed to Marie-Pierre Préziosi.

4 recordsLinked to original sources

PubMed2004

Estimating heterogeneous transmission with multiple infectives using MCMC methods.

We developed a general procedure for estimating the transmission probability adjusting for covariates when susceptibles are exposed to several infectives concurrently and taking correlation within transmission units into account. The procedure is motivated by a study estimating efficacy of pertussis vaccination based on the secondary attack rate in a rural sub-Saharan community (Niakhar, Senegal) and illustrated with simulations. The procedure is also appropriate to estimate the pairwise transmission probability in transmission studies of live vaccine virus in a collection of transmission units, such as day-care centres or retirement centres. Previously, analyses either excluded transmission units with multiple infectives or ignored co-infectives. Excluding transmission units with multiple infectives is statistically less efficient and ignoring co-infectives can lead to biased estimation. Modelling is carried out by regressing the latent pairwise transmission probability from each infective to a susceptible on covariates and specifying a transmission linkage function linking the latent pairwise transmission probability to the overall transmission probability. Parameters are estimated using Markov chain Monte Carlo methods.

Bayes Theorem↗

PubMed2003

Effects of pertussis vaccination on disease: vaccine efficacy in reducing clinical severity.

We estimated the effectiveness of pertussis vaccination in reducing the clinical severity of breakthrough disease among vaccinated individuals from a comprehensive follow-up study of a community of 30,000 residents of Niakhar, Senegal, in 1993. A physician examined all children with potential pertussis (cough of >7 days' duration). Samples were collected from 97% of these children for culture or serologic testing as part of the active surveillance for a pertussis vaccine trial. Cases of pertussis were defined by confirmation through culture or serologic testing or by a history of contact with a person with culture-confirmed pertussis. Among children with confirmed cases, severity of illness was assessed according to a scale that combined clinical signs and symptoms. The efficacy of the vaccine in reducing disease severity was 48% (95% confidence interval, 39%-55%) among children vaccinated with 3 doses of whole-cell (67%) or acellular (32%) vaccine. Primary cases were more severe than secondary cases in residential compounds. Pertussis vaccination is effective in reducing the severity of illness.

Bordetella pertussis↗

PubMed2003

Effects of pertussis vaccination on transmission: vaccine efficacy for infectiousness.

We estimated the effect of pertussis vaccination on reducing transmission from vaccinated breakthrough cases from a comprehensive follow-up of a community of 30,000 residents in Niakhar, Senegal. Using a wide spectrum of case definitions, vaccine efficacy was estimated as 1 - the ratio of secondary attack rates (SAR) in all households with cases during the calendar year 1993, a pertussis epidemic year. Vaccine efficacy for infectiousness (VEi) was 85% (95% confidence interval (CI), 46-95%) for children vaccinated with three doses of a whole-cell (WC; 94%) or an acellullar (6%) pertussis vaccine, with pertussis defined as a cough >/=21 days with paroxysms confirmed by culture, serology, or contact with a culture-confirmed person. It was high for all case definitions. Partial vaccination reduced infectiousness. Pertussis vaccination is highly effective in reducing transmission from vaccinated breakthrough cases.

Child↗

PubMed2002

Epidemiology of pertussis in a West African community before and after introduction of a widespread vaccination program.

The control of pertussis remains a worldwide concern. Little has been documented about its epidemiology in Africa. The authors have studied pertussis in a prospective cohort of children in a rural West African community over a 13-year period comprising time before and after introduction of a vaccination program. Children under age 15 years who were residents of the Niakhar study area in Senegal were followed prospectively between January 1984 and December 1996 for the occurrence of pertussis. Morbidity and mortality rates were extremely high before the launch of immunization. Crude incidence was 183 per 1,000 child-years at risk under age 5 years, with a 2.8% case-fatality rate. After the introduction of the vaccination program, overall incidence dropped rapidly and dramatically-by 27% after 3 years and 46% after 6 years. The decline in incidence involved all age groups but was most substantial in the group under age 5 years and was particularly pronounced in unvaccinated infants. The median age of acquisition of the disease rose steadily with population vaccine coverage. This study shows the tremendous magnitude of the disease burden in children and the rapid decline after vaccination, and it suggests a strong herd-immunity effect.

Adolescent↗