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Biomedical subjects

F Simondon

Publications and source records attributed to F Simondon.

At least 19 recordsLinked to original sources
PubMed2006

Early short-term infant food supplementation, maternal weight loss and duration of breast-feeding: a randomised controlled trial in rural Senegal.

OBJECTIVE: Early supplementation of breastfed infants may have consequences both for the mother and the child. We hypothesised that it would result in decreased maternal weight loss and in shorter durations of breastfeeding and birth intervals. DESIGN: Controlled randomised population-based trial. SETTING: Six villages in the Sine area of Senegal, West Africa. SUBJECTS: Healthy breastfed infants and their mothers, 68 controls and 66 supplemented infants at randomization. INTERVENTION: Supplementation with high-energy, nutrient dense food from 4 to 7 months of age, twice daily under supervision of field workers. Both controls and supplemented infants were free to eat other complementary foods. Maternal weight was measured monthly. Dates of breastfeeding cessation and of subsequent births were collected prospectively through weekly demographic surveillance, and were analysed using Cox's regression models and 'intent-to-supplement' approach. RESULTS: Mean maternal weight gain from 4 to 7 months postpartum tended to be greater in the supplemented group (+0.25 kg/months, 95% confidence interval (CI): -0.07, +0.57). Supplemented infants were breastfed for significantly longer durations than controls (medians: 24.9 and 23.7 months, respectively, P: 0.034). Their adjusted hazard ratio (HR) for breastfeeding cessation was 0.59 (95% CI: 0.40, 0.89). Their mothers had a lower risk of a new birth than mothers of controls (adjusted HR: 0.57, 95% CI: 0.36, 0.92). CONCLUSIONS: Early short-term infant supplementation tended to decrease maternal postpartum weight loss, but it increased, rather than shortened, the duration of breastfeeding and birth interval. SPONSORSHIP: This study was supported by a grant from the French Ministry of Research (Grant 92L0623).

Adult↗
PubMed2004

Non-specific effects of vaccination on child survival: prospective cohort study in Burkina Faso.

OBJECTIVE: To study the effect of vaccination on mortality before 2 years of age in a developing country. DESIGN: Prospective cohort study. SETTING: Rural communities in Burkina Faso. PARTICIPANTS: 9085 children born in the study area between 1985 and 1993. MAIN OUTCOME MEASURE: Child death rate. RESULTS: Mortality before 2 years of age was lower in children who had been vaccinated: those vaccinated with BCG only had significantly lower mortality (risk ratio for vaccinated v unvaccinated children 0.37, 95% confidence interval 0.29 to 0.48) as did those vaccinated with diphtheria, tetanus, and pertussis only (0.24, 0.13 to 0.43). The second dose of diphtheria, tetanus, and pertussis was not associated with lower mortality (0.80, 0.58 to 1.12). CONCLUSION: Vaccination with diphtheria, tetanus, and pertussis as well as BCG is associated with better survival of children up to 2 years of age.

BCG Vaccine↗
PubMed2003

Change in body water distribution index in infants who become stunted between 4 and 18 months of age.

OBJECTIVE: To evaluate body composition changes using bioelectrical impedance analysis and skinfold thickness measurements in infants from tropical areas who become stunted between 4-18 months of age. DESIGN AND MEASUREMENTS: Follow-up study. Extracellular water to total body water ratio index (length(2)/resistance at low to high frequency), peripheral fat (tricipital and subscapular skinfold thickness), and length-for-age index were studied at 4 and 18 months of age. SETTINGS: Low-income areas in four tropical regions (Congo, Senegal, Bolivia and New Caledonia). SUBJECTS: Infants were included in the analysis provided they were neither stunted nor wasted at 4 months. Two groups of infants were compared, those that were stunted at 18 months (n=61) or not (n=170). RESULTS: The extracellular water to total body water ratio index and the sum of skinfold thickness measurements were similar in the two groups at 4 months, and only the extracellular water to total body water ratio index was significantly different at 18 months. When no stunting appeared between 4 and 18 months, the change in the extracellular water to total body water ratio index was not linked with variations in length-for-age, and presented the expected pattern of variation in body water compartments. When stunting occurred, variation in length-for-age was related to significant changes in the extracellular water to total body water ratio index, the biggest increase in the proportion of extracellular water being found in the most stunted infants. Variations in the sum of the two skinfold thickness measurements presented the expected pattern for the 4-18 months growth and did not differ between the two groups. CONCLUSIONS: Multifrequency resistances suggested that stunting was associated with a lack of the expansion of the intracellular compartment that is expected during normal growth of cell mass, together with preserved fat mass. SPONSORSHIPS: Supported by grant 92L0623 from the French Ministry of Research, and by Institut de Recherche pour le Développement (IRD).

Adipose Tissue↗
PubMed2001

The frailty hypothesis revisited: mainly weak children die of measles.

It has been suggested that measles infection mainly kills frail children who are likely to die anyhow of other infections. If that were true, the proportion of frail children should increase after the introduction of measles vaccination and post-measles mortality compared with mortality in uninfected children should increase when the case fatality declines and frail children are no longer dying of measles. The latter deduction was investigated in Niakhar, Senegal, where the measles case fatality has declined markedly. Measles has been studied in Niakhar during 12 years from 1983 to 1994. We compared long-term mortality after measles infection in periods with both high and low case fatality. The acute measles case fatality rate (CFR) declined from 6.5% in 1983-1986 to 1.5% in 1987-1994, an age-adjusted decline of 66% (RR=0.34 (0.19-0.58)). Between 1983-1986 and 1987-1994, mortality in the first year after measles infection declined by 35% (RR=0.65 (0.37-1.16)), the pattern being the same in the second and third year after infection (RR=0.63 (0.33-1.21)). This reduction could not be related to introduction of immunization, treatment of measles with Vitamin A, or prophylactic use of antibiotics. Controlling for age, immunization, and season, the decline in post-measles mortality was similar to the fall in non-measles-related mortality between the two periods (mortality rate ratio=0.72 (0.64-0.80)). Since the mortality decline in survivors of measles was as large as the decline in mortality among uninfected children, reduction in acute measles mortality did not lead to accumulation of frail children. We doubt measles infection ever eliminated mainly weak children; it always killed a broad spectrum of children, most of whom were "fit to survive". Hence, it seems unlikely that measles vaccination has contributed to the survival of more frail children.

Child↗
PubMed2001

Breast-feeding is associated with improved growth in length, but not weight, in rural Senegalese toddlers.

BACKGROUND: Prolonged breast-feeding is frequently associated with malnutrition in less-developed countries, even after adjustment for socioeconomic confounders. However, in rural Senegal, breast-feeding is prolonged when the child is stunted. OBJECTIVE: We aimed to test whether the lower height-for-age of children weaned late is explained by their height before weaning or whether prolonged breast-feeding is associated with impaired growth. DESIGN: A cohort of 443 Senegalese children recruited from dispensaries at 2 mo of age were visited in their homes at 6-mo intervals when they were approximately 1.5 to 3 y of age. Weight, length, arm circumference, and triceps skinfold thickness were measured. Six-month increments were analyzed in relation to breast-feeding (breast-fed compared with weaned children or breast-feeding duration), season, and maternal housing with use of multiple linear regression. RESULTS: The mean duration of breast-feeding was 24.1 mo (quartiles 1 and 3: 21.9 and 26.4). Height-for-age at the age of 3 y was negatively associated with age at weaning (P < 0.01), but this association disappeared after adjustment for height-for-age in infancy. Length increments were significantly greater in both the second and third years of life in children breast-fed for longer durations (P < 0.05) and tended to be greater in breast-fed than in weaned children in the second year of life (P = 0.05). In the third year of life, breast-fed children had greater length increments than did weaned children in the subgroup with poor housing (P for interaction < 0.05). Growth in weight did not differ significantly according to breast-feeding. CONCLUSION: Prolonged breast-feeding improved linear growth, and the negative relation between height-for-age and duration of breast-feeding was due to reverse causality.

Analysis of Variance↗
PubMed2001

Children's height, health and appetite influence mothers' weaning decisions in rural Senegal.

BACKGROUND: In many developing countries, breastfed children have a lower nutritional status than those weaned from 12 months of age. Reverse causality, that is, earlier weaning of healthy and well-nourished children, is a possible explanation. METHODS: Maternal reasons for early and late weaning were investigated in a cohort of 485 rural Senegalese children using structured interviews during two rounds at the ages of 18--28 and 23--33 months, respectively. Length, weight and height were assessed, and dates of weaning were monitored. RESULTS: The mean duration of breastfeeding was 24.1 months (quartiles 21.9 and 26.3). Two-thirds of mothers of breastfed children under 2 stated that they would wean at the age of 2, while for breastfed children aged 2 years, a 'tall and strong' child was the most prevalent criterion. The main reasons for weaning prior to 2 years (N = 244) were that the child ate well from the family plate (60%), that the child was 'tall and strong' (46%) and maternal pregnancy (35%). The main reasons for weaning later than the age of 2 were: a 'little, weak' child (33%), food shortage (25%), illness of the child (24%) and refusal of family food (14%, N = 120). Children breastfed above the age of 2 because they were 'small and weak' had lower mean height-for-age and a greater prevalence of stunting than children breastfed late for other reasons (P < 0.0001). CONCLUSION: The habit of postponing weaning of stunted children very likely explains why breastfed children have lower height-for-age than weaned children in this setting.

Age Factors↗
PubMed2001

Decline of infant and child mortality rates in rural Senegal over a 37-year period (1963-1999).

BACKGROUND: In spite of an improving trend, childhood mortality in rural sub-Saharan Africa remains high and has recently risen in some countries. The factors associated with the long-term decline in childhood mortality are poorly known, due to a lack of data. METHODS: A Senegalese rural population has been under demographic surveillance since 1963. Infant and under-5 mortality rates were calculated for different periods to generate a long-term trend in childhood mortality. Evolution of age and seasonal patterns of mortality were observed. FINDINGS: During the observation period (1963-1999), infant and under-5 mortality rates decreased from 223 per thousand to 80 per thousand and 485 per thousand to 213 per thousand , respectively, with a constant annual rate of decline in the probability of dying since the 1960s (-3.7% and -3.1%, respectively). The age pattern of the under-5 mortality changed drastically, with a large decrease in the death rate between 6 and 24 months of age (from 321 per thousand to 87 per thousand ). This change took place during the 1970s. The seasonal variation, characterized by a greater proportion of deaths during the rainy season, was very marked during the 1960s, then decreased during the 1980s but it has tended to increase again in the 1990s, particularly among children 1-4 years old. CONCLUSION: This study confirms the long-term trend of decrease in child mortality in rural West Africa. Historical knowledge on healthcare developments suggests that immunizations have contributed to the decrease and the change in the age pattern. The re-emergence of malaria seems the most likely explanation for the recent rebound in seasonal variation. Attention to immunization and malaria should continue to be a priority.

Age Distribution↗
PubMed2000

[Genetic evolution under vaccine pressure: the Bordetella pertussis model].

A possible genetic selective pressure related to the long-term use of vaccines has been the object of recent theoretical thought and publications. For more than thirty years, an effective vaccine has been in use against whooping cough on a wide scale basis in several countries. Thus, the Bordetella pertussis model may contribute to the analysis of an evolutionary risk linked to the vaccine. To maintain and improve the control of whooping cough, better vaccination coverage must be achieved in countries where prevalence is low. In countries where high vaccination coverage has been achieved over a long period, a trend toward the resurgence of the disease has been observed. Efforts are therefore now being directed toward primary vaccination and boosters. These two targets require new vaccines with fewer side effects. Outbreaks in highly vaccinated populations have been reported, raising the issues of vaccine efficacy, of the long-term effect of vaccines on the transmission of the disease, and of genetic selective pressure. Time trend modifications of circulating strains related to vaccination practices and vaccine types have been observed and are compatible with a selective pressure of the vaccine on related pathogens. However, evidence for a causal relation is lacking. In order to monitor and understand the various effects the vaccine may be having on the effectiveness of immunisation against whooping cough, further surveillance is needed, integrating a standardised characterisation of circulating strains and vaccines by way of a space-time sampling model.

Biological Evolution↗
PubMed1999

Role of schools in the transmission of measles in rural Senegal: implications for measles control in developing countries.

Patterns of measles transmission at school and at home were studied in 1995 in a rural area of Senegal with a high level of vaccination coverage. Among 209 case children with a median age of 8 years, there were no deaths, although the case fatality ratio has previously been 6-7% in this area. Forty percent of the case children had been vaccinated against measles; the proportion of vaccinated children was higher among secondary cases (47%) than among index cases (33%) (prevalence ratio = 1.36, 95% confidence interval (CI) 1.04-1.76). Vaccinated index cases may have been less infectious than unvaccinated index cases, since they produced fewer clinical cases among exposed children (relative risk = 0.55, 95% CI 0.29-1.04). The secondary attack rate was lower in the schools than in the homes (relative risk = 0.31, 95% CI 0.20-0.49). The school outbreaks were protracted, with 4-5 generations of cases being seen in the two larger schools. Vaccine efficacy was found to be 57% (95% CI -23 to 85) in the schools and 74% (95% CI 62-82) in the residential compounds. Measles infection resulted in a mean of 3.8 days of absenteeism per case, though this did not appear to have an impact on the children's grades. Among the index cases, 56% of children were probably infected by neighbors in the community, and 7% were probably infected at health centers, 13% outside the community, and 24% in one of the three schools which had outbreaks during the epidemic. However, most of the school-related cases occurred at the beginning and therefore contributed to the general propagation of the epidemic. To prevent school outbreaks, it may be necessary to require vaccination prior to school entry and to revaccinate children in individual schools upon detection of cases of measles. Multidose measles vaccination schedules will be necessary to control measles in developing countries.

Absenteeism↗
PubMed1999

Effect of subclinical infection on maintaining immunity against measles in vaccinated children in West Africa.

BACKGROUND: Despite a high coverage with measles vaccines in parts of west Africa, epidemics of measles occur with reduced severity in an increasing proportion of older children who have been vaccinated. We examined the effect of exposure to natural measles on immunity in vaccinated children. METHODS: Our study was carried out in 1992 during an epidemic of measles in Niakhar, a rural area of Senegal with about 27,000 inhabitants who mostly live in compounds that include several households; within each household people live in different huts. Vaccine coverage in Niakhar was 81% at the time of our study. We measured haemagglutinin-inhibiting antibody at exposure and twice thereafter (after 4-5 weeks and at 6 months) in 36 vaccinated and 87 unvaccinated children. The frequency of measles and subclinical measles--defined as a four-fold or greater rise in antibody titre without clinical signs or symptoms--was related to intensity of exposure according to whether the index case was in the same hut, household, or compound. FINDINGS: Clinical measles occurred in 20 (56%) of 36 unvaccinated children and in one (1%) of 87 vaccinated children. Subclinical measles occurred in 39 (45%) of 86 vaccinated children who were exposed to measles and in four (25%) of 16 unvaccinated children. The frequency was inversely related to pre-exposure antibody concentration (p<0.001 for trend) and directly related to intensity of exposure (p=0.002 for trend). Antibody concentrations in subclinical cases increased on average by 45-fold and remained raised for at least 6 months. INTERPRETATION: Increased antibody titre after subclinical measles may be common in vaccinated children in West Africa where the intensity of exposure is high. As measles vaccination coverage increases, the circulation of wild measles will decrease, and vaccine-induced antibody is less likely to be boosted. Thus, new epidemics, albeit milder in form, may occur in vaccinated areas which should be recognised in campaigns to eradicate measles.

Adolescent↗
PubMed1999

Randomised study of the possible adjuvant effect of BCG vaccine on the immunogenicity of diphtheria-tetanus-acellular pertussis vaccine in Senegalese infants.

Following a study in Senegal (1990-1995) in which the relative efficacy of a diphtheria-tetanus-acellular pertussis vaccine (DTaP) was compared with that of a diphtheria-tetanus-whole-cell pertussis vaccine in children given a simultaneous injection of Bacille Calmette-Guérin (BCG) vaccine, this subsequent study was conducted to evaluate the possible adjuvant effect of the BCG vaccine on acellular pertussis vaccine components. A second objective was to compare the immunogenicity of these components when administered in accordance with a 2-4-6-month (spaced) schedule or an accelerated 2-3-4-month schedule. In all, 390 healthy Senegalese infants were randomly divided into three groups of 130 infants. Antibodies to acellular pertussis components were measured in serum samples obtained within 2 days of the first DTaP dose and 1 month after the third dose. BCG vaccine, given simultaneously with the DTaP vaccine, did not influence the immunogenicity of the acellular pertussis vaccine components when compared with separate administration of the two vaccines. Infants immunised according to a 2-4-6-month schedule had a significantly higher immune response than those immunised according to a 2-3-4-month schedule with respect to the response to pertussis toxoid assessed by seroneutralisation on Chinese hamster ovary cells (P<0.0001). These results suggest that BCG and DTaP vaccines can be given simultaneously without interference or enhancement and that more optimal immunogenicity is achieved with an extended than with an accelerated schedule.

Antibodies, Bacterial↗
PubMed1999

Capture-recapture method for estimating misclassification errors: application to the measurement of vaccine efficacy in randomized controlled trials.

BACKGROUND: The measure of efficacy is optimally performed by randomized controlled trials. However, low specificity of the judgement criteria is known to bias toward lower estimation, while low sensitivity increases the required sample size. A common technique for ensuring good specificity without a drop in sensitivity is to use several diagnostic tests in parallel, with each of them being specific. This approach is similar to the more general situation of case-counting from multiple data sources, and this paper explores the application of the capture-recapture method for the analysis of the estimates of efficacy. METHOD: An illustration of this application is derived from a study on the efficacy of pertussis vaccines where the outcome was based on > or =21 days of cough confirmed by at least one of three criteria performed independently for each subject: bacteriology, serology, or epidemiological link. Log-linear methods were applied to these data considered as three sources of information. RESULTS: The best model considered the three simple effects and an interaction term between bacteriology and epidemiological linkage. Among the 801 children experiencing > or =21 days of cough, it was estimated that 93 cases were missed, leading to a corrected total of 413 confirmed cases. The relative vaccine efficacy estimated from the same model was 1.50 (95% confidence interval: 1.24-1.82), similar to the crude estimate of 1.59 and confirming better protection afforded by one of the two vaccines. CONCLUSION: This method allows supporting analysis to interpret primary estimates of vaccine efficacy.

Adolescent↗
PubMed1999

Seroconversions in unvaccinated infants: further evidence for subclinical measles from vaccine trials in Niakhar, Senegal.

BACKGROUND: Increases in measles antibodies without rash-illnesses have been documented in previously vaccinated children exposed to measles cases. The phenomenon has been incompletely evaluated in young unvaccinated infants with immunity of maternal origin. METHODS: Monthly cohorts of newborns were prospectively randomized to vaccine and placebo control groups during a trial of high-titre vaccines in Niakhar, Senegal. Measles antibodies were assayed in blood samples of enrolled children collected at 5 months old, when controls received a placebo injection, and at 10 months, when the placebo group was given measles vaccine. Intensive prospective surveillance for measles was conducted throughout the trial. RESULTS: One-fifth (n = 53) of the placebo controls seroconverted, with known exposure to a measles case in only three of them. None of the seroconverters developed a measles-like rash. Sixteen-fold or greater increases in titres were noted in about one-quarter of them. Compared with placebo controls who did not seroconvert, seroconverters were more likely to have had exposure to a measles case and to travel, more likely to be boys than girls, and had significantly lower baseline antibody titres. Measles was endemic in the study area throughout the trial. Seroconversions did not adversely effect subsequent nutritional indices or mortality. CONCLUSIONS: Although laboratory errors and inadvertent injection of vaccine rather than placebo may have played some role, they do not fully explain the above observations, which are consistent with subclinical measles in the seroconverters. The possible role of subclinical measles in occult transmission, its potential effect on the type and duration of subsequent immunity, and its impact on response to primary vaccination need to be determined.

Analysis of Variance↗
PubMed1999

Increased long term mortality associated with rash after early measles vaccination in rural Senegal.

OBJECTIVES: To examine whether clinical symptoms, including rash, were more common after measles immunization compared with placebo and to study the association between postvaccination symptoms and later mortality. DESIGN: Examination of side effects in the 3 weeks after immunization in a trial of high titer and standard titer measles vaccines. PATIENTS: Two hundred twenty-four children randomly selected to be included in the surveillance for diarrhea, fever and rash. RESULTS: There was no difference in fever and diarrhea between recipients of high titer vaccines and recipients of placebo. However, high titer recipients tended to have more measles-like rashes than placebo recipients [relative risk, 2.12 (range, 0.90 to 5.03)]. Among recipients of high titer vaccines, children who presented a rash had higher mortality in the following 5 to 7 years than those who did not develop rash [mortality rate ratio, 3.85 (range, 1.52 to 9.79)]. High titer recipients without a rash had the same mortality as children in the placebo group who were given standard doses of measles vaccine at 10 months of age [mortality rate, 0.76 (range, 0.35 to 1.62)]. CONCLUSIONS: These observations suggest that in this particular study, rash after high titer measles vaccine may identify children who received a particularly high dose of vaccine or children with more severe and persistent postvaccination immunosuppression. Whether high titer vaccine is more likely than standard titer measles vaccine to provoke such reaction is not known, given that we did not compare side effects after different titers of measles vaccine. Future trials of live measles vaccine should monitor the development of rash.

Cause of Death↗
PubMed1999

Poor serologic responses five to seven years after immunization with high and standard titer measles vaccines.

BACKGROUND: Few data exist on the persistence of measles antibodies after vaccination of West African infants. Therefore we examined measles antibody titers 5 to 7 years after children in rural Senegal had received high titer Edmonston-Zagreb (EZ-HT), high titer Schwarz (SW-HT) or standard titer Schwarz (SW-STD) measles vaccines in infancy. METHODS: Children had received either high titer vaccines at 5 months of age or standard titer at 10 months of age. Finger prick blood samples were tested for measles antibody 5 to 7 years later by the hemagglutinin inhibition test. RESULTS: Persistence of antibody after high titer vaccines was poor with the result that 39 and 50% of the EZ-HT and the SW-HT groups had low titers of hemagglutinin inhibition measles antibodies (< or =125 mIU/ml). Nineteen percent of the children in the SW-STD group had low titers which is a lower prevalence than in the high titer groups [relative risk (95% confidence intervals), 0.05 (0.28 to 0.88) vs. EZ-HT; relative risk, 0.38 (0.22 to 0.66) vs. SW-HT]. Geometric mean (95% confidence interval) antibody titers in children with detectable values were 616 (435 to 871) in the EZ-HT, 1106 (616 to 1866) in the SW-HT and 1271 (871 to 1741) mIU/ml in the SW-STD groups, respectively. Multivariant regression analysis showed that mean titers were 2.00 (1.03 to 3.89) times higher for children with low prevaccination antibody titers (< or =125 mIU/ml) and 3.06 (1.90 to 4.94) times higher if blood was collected in the rainy season. INTERPRETATION: Given the rapid decline in antibody titers over a 5- to 6-year period in an area where measles vaccine coverage was high, it seems likely that multiple dose immunization schedules will be needed in the future to maintain protective antibody concentrations (>125 mIU/ml) in West Africa. The role of subclinical boosting by exposure to natural measles and the possible role of malaria, which increases immunoglobulin turnover, in influencing long term antibody persistence after vaccination deserve further investigation.

Antibodies, Viral↗
PubMed1998

Impact of chloroquine resistance on malaria mortality.

Over 12 years, from 1984 to 1995, we conducted a prospective study of overall and malaria specific mortality among three rural populations in the Sahel, savanna and forest areas of Senegal. The emergence of chloroquine resistance has been associated with a dramatic increase in malaria mortality in each of the studied populations. After the emergence of chloroquine resistance, the risk of malaria death among children 0-9 years old in the three populations was multiplied by 2.1, 2.5 and 5.5, respectively. This is the first study to document malaria mortality at the community level in Africa before and after the emergence of chloroquine resistance. Findings suggest that the spread of chloroquine resistance has had a dramatic impact on the level of malaria mortality in most epidemiological contexts in tropical Africa.

Antimalarials↗