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C Viboud

Publications and source records attributed to C Viboud.

11 recordsLinked to original sources
PubMed2005

More on RotaShield and intussusception: the role of age at the time of vaccination.

BACKGROUND: RotaShield, a vaccine intended to prevent severe rotavirus diarrhea, was withdrawn in July 1999, 9 months after it became available in the United States, because of a temporal association with intussusception events that occurred in vaccinated infants. We explore here the effect of age on the risk of intussusception. METHODS: We reanalyzed a case-control database of the Centers for Disease Control and Prevention by use of a 21-day window, to define vaccine-associated events. We obtained data on vaccine use from the National Immunization Survey and estimated the age-stratified background incidence of intussusception by use of Healthcare Cost and Utilization Project data. We combined these data to estimate how absolute risk varies with age and to model the projected population-attributable risk associated with 3 different vaccination schedules. RESULTS: We found that the incidence of intussusception associated with the first dose of vaccine increased with age. Infants > or = 90 days old accounted for 80% of cases of intussusception associated with a first dose but had received only 38% of first doses. Modeling of the recommended schedule of vaccination at ages 2, 4, and 6 months projected 1 intussusception event/11,000-16,000 vaccine recipients; modeling of a 2-dose schedule beginning in the neonatal period projected 1 intussusception event/38,000-59,000 vaccine recipients. CONCLUSIONS: The practice of initiating immunization after age 90 days, which we call "catch-up" vaccination, contributed disproportionately to the occurrence of intussusception associated with the use of RotaShield. A fully implemented 2-dose vaccination schedule begun during the neonatal period would lead to, at most, a 7% increase in the incidence of intussusception above the annual background incidence.

Age Factors↗
PubMed2005

[Prevalence and management of heart failure in France: national study among general practitioners of the Sentinelles network].

BACKGROUND: Epidemiological data on heart failure's epidemiology in France are scarce and mostly hospital based. The present study's objective is to estimate the prevalence of heart failure (HF) and its management, in subjects aged 60 years and older seen by the French general practitioners (GP). METHODS: A standardised questionnaire was mailed to 900 GPs of the Sentinelles network, requiring answers for any patient aged 60 years and more, seen on a randomly assigned single day of year 2002. National census and health insurance data were used to estimate prevalence. RESULTS: 434 GPs answered, reporting data for 1797 patients aged 60 years and more. The 214 patients with HF, aged 79 years on average, had been seen by a cardiologist in 95% of cases. Results of an echocardiography was available for 58% of HF patients. Compared to non-HF patients, patients with HF were significantly more dependent, more frequently requiring home visit of the GP and more frequently hospitalised (p < 0.001, age adjusted). All the 42% HF patients with a reported left ventricle ejection fraction lower than 40% were treated with an angiotensin converting enzyme inhibitor or an angiotensin receptor inhibitor. The prevalence of HF among patients aged 60 years and older was estimated at 11.9% in general practice (95% confidence interval: 10.5-13.5), and at 2.19% (1.9-2.5) in the general population. The prevalence increased with age, over 20% in persons aged 80 years and more. CONCLUSION: HF in patients aged 60 years and more seen in general practice in France is characterised by a high prevalence and medical consumption in terms of required number of hospitalisation and GP's home visit. For the GP, the diagnosis of HF relies on the cardiologist more than on an echocardiography. The therapeutic management seems to fit the actual recommendations.

Aged↗
PubMed2004

A Bayesian MCMC approach to study transmission of influenza: application to household longitudinal data.

We propose a transmission model to estimate the main characteristics of influenza transmission in households. The model details the risks of infection in the household and in the community at the individual scale. Heterogeneity among subjects is investigated considering both individual susceptibility and infectiousness. The model was applied to a data set consisting of the follow-up of influenza symptoms in 334 households during 15 days after an index case visited a general practitioner with virologically confirmed influenza. Estimating the parameters of the transmission model was challenging because a large part of the infectious process was not observed: only the dates when new cases were detected were observed. For each case, the data were augmented with the unobserved dates of the start and the end of the infectious period. The transmission model was included in a 3-levels hierarchical structure: (i) the observation level ensured that the augmented data were consistent with the observed data, (ii) the transmission level described the underlying epidemic process, (iii) the prior level specified the distribution of the parameters. From a Bayesian perspective, the joint posterior distribution of model parameters and augmented data was explored by Markov chain Monte Carlo (MCMC) sampling. The mean duration of influenza infectious period was estimated at 3.8 days (95 per cent credible interval, 95 per cent CI [3.1,4.6]) with a standard deviation of 2.0 days (95 per cent CI [1.1,2.8]). The instantaneous risk of influenza transmission between an infective and a susceptible within a household was found to decrease with the size of the household, and established at 0.32 person day(-1) (95 per cent CI [0.26,0.39]); the instantaneous risk of infection from the community was 0.0056 day(-1) (95 per cent CI [0.0029,0.0087]). Focusing on the differences in transmission between children (less than 15 years old) and adults, we estimated that the former were more likely to transmit than adults (posterior probability larger than 99 per cent), but that the mean duration of the infectious period was similar in children (3.6 days, 95 per cent CI [2.3,5.2]) and adults (3.9 days, 95 per cent CI [3.2,4.9]). The posterior probability that children had a larger community risk was 76 per cent and the posterior probability that they were more susceptible than adults was 79 per cent.

Adolescent↗
PubMed2004

Modelling responses to a smallpox epidemic taking into account uncertainty.

Epidemiology and modelling are currently under pressure to build consistent scenarios of control in case of deliberate release of biological weapons. In order to assess the key parameters for the control of a smallpox outbreak in a large city (2 million inhabitants), we built a stochastic model to simulate the course of an epidemic controlled by ring vaccination and case isolation. Assuming a reference scenario with 100 index cases and implementation of intervention 25 days after the attack, the model forecasts an epidemic of 730 cases with an epidemic duration of 240 days. Setting intervention 20 days later would result in an almost fourfold increase in the epidemic size. A multivariate sensitivity analysis has selected three key parameters: the basic reproduction number (i.e. the number of secondary cases infected by one case in an entirely susceptible population, equal to 3 in the reference scenario), time to intervention, and proportion of traced and vaccinated contacts.

Algorithms↗
PubMed2003

Non-steroidal anti-inflammatory drugs as a risk factor for acute diarrhoea: a case crossover study.

BACKGROUND AND AIMS: Several cases of acute colitis induced by non-steroidal anti-inflammatory drugs (NSAIDs) have been reported but the general role of recent NSAID intake as a risk factor for acute diarrhoea has not been studied to date. The aim of our study was to determine whether the risk of acute diarrhoea is increased by NSAIDs in a prospective series of acute diarrhoea cases which were seen by general practitioners in France and were serious enough to require a stool culture. Patients, physicians, and methods: A total of 285 consecutive patients with acute diarrhoea, seen by Sentinel general practitioners (GPs) between December 1998 and July 1999, were enrolled in a case crossover study in which each case served as his/her own control. GPs collected information on exposure to NSAIDs during the four month period preceding the onset of diarrhoea. The relative risk of NSAID related acute diarrhoea was estimated by comparing exposure to NSAIDs during a risk period preceding the onset of diarrhoea with exposure during the first part of the four month observation period. Three risk periods lasting for one, three, and six days before the onset of diarrhoea were considered. RESULTS: The relative risks of acute diarrhoea due to recent NSAID intake were increased for all three risk periods. These risks and their confidence intervals were 2.9 (1.4-6.1) for the one day risk period, 2.7 (1.4-5.1) for the three day period, and 3.3 (2.0-5.4) for the six day period. CONCLUSION: Recent NSAID intake emerges as a risk factor for acute diarrhoea. We suggest that acute diarrhoea seen in general practice, and not only acute colitis seen by gastroenterologists, should be considered as a potential complication of recent NSAID intake.

Acute Disease↗
PubMed2001

Nevirapine and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis.

OBJECTIVE: To draw attention to the many cases of Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) related to nevirapine detected in a multinational case-control study of SJS and TEN. METHODS: Actively detected cases and matched hospital controls were interviewed for exposure to drugs and other risk factors. Data were analysed with case-control and case-crossover methods. RESULTS: Between May 1997 and November 1999, a diagnosis of SJS or TEN was established in 246 patients. Eighteen were known to be infected by HIV-1 (7.3%), 15 out of these 18 had been exposed to nevirapine. The reaction began 10-240 days after the introduction of nevirapine (median, 12 days) and all patients had received escalating doses. In 10 patients the reaction occurred with the initial dosage. All but one patients received simultaneously a variety of other antiretroviral agents but no specific drug combination emerged, and nevirapine was the only drug significantly associated with an increased risk of SJS or TEN in HIV-infected persons [odds ratio, 62 (10.4; +infinity) in the case-control analysis; odds ratio, +infinity (2.8; +infinity) in the case-crossover analysis]. CONCLUSIONS: In European countries the risk of SJS or TEN in the context of HIV infection appears to be associated with nevirapine. The respect of a lead-in period does not appear to prevent SJS or TEN. Because of the severity of these reactions and the long elimination half-life of nevirapine, we suggest discontinuation of the drug as soon as any eruption occurs.

Adult↗
PubMed2001

Comparison of the statistical efficiency of case-crossover and case-control designs: application to severe cutaneous adverse reactions.

Although case-crossover analyses have lately emerged as an alternative to case-control analyses in epidemiological studies, it is not yet known in which situations they give reliable conclusions. In this work, the case-crossover and the case-control designs were first compared on the basis of a dataset from a published study of severe cutaneous adverse reactions resulting from drug exposures of various durations and prevalences of use (245 cases, 1147 controls, and exposures to 23 drug classes). Next, the statistical efficiency of each design was compared via Monte Carlo simulations. Eight of the 13 risk factors identified by case-control analysis of the published data were also identified by the case-crossover analysis, with fairly good agreement on ranks of risk estimates (Spearman's correlation coefficient = 0.71, P < 0.001 ). Simulation studies showed that for relative risks below 8, the case-crossover design (250 cases, 4 control periods/case) had a higher power than the case-control design (250 cases, 4 controls/case), and that the case-crossover design was more conservative than the case-control design for prevalences of drug use below 10%. We conclude that the case-crossover design is not suitable for long-term exposures, but is an appropriate alternative for assessing rare risks associated with transient to short-term exposures.

Case-Control Studies↗
PubMed2000

Automatic coding of reasons for hospital referral from general medicine free-text reports.

Although the coding of medical data is expected to benefit both patients and the health care system, its implementation as a manual process often represents a poorly attractive workload for the physician. For epidemiological purpose, we developed a simple automatic coding system based on string matching, which was designed to process free-text sentences stating reasons for hospital referral, as collected from general practitioners (GPs). This system relied on a look-up table, built up from 2590 reports giving a single reason for referral, which were coded manually according to the International Classification of Primary Care (ICPC). We tested the system by entering 797 new reasons for referral. The match rate was estimated at 77%, and the accuracy rate, at 80% at code level and 92% at chapter level. This simple system is now routinely used by a national epidemiological network of sentinel physicians.

Confidence Intervals↗