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Biomedical subjects

J Chotard

Publications and source records attributed to J Chotard.

17 recordsLinked to original sources
PubMed1994

Do bedbugs transmit hepatitis B?

An intervention study was done over two years in seven Gambian villages to determine the contribution of bedbugs to hepatitis B transmission. In addition, fortnightly questionnaires were completed for each child to assess other possible routes of transmission. The intervention, insecticide spraying of the child's dwelling, was highly effective in reducing exposure to bedbugs but there was no effect on hepatitis B infection. No other risk factor for transmission was identified despite a consistent village-to-village variation in the rate of childhood infection. The major mode of transmission of hepatitis B in childhood remains unknown.

Animals↗
PubMed1993

Efficacy of hepatitis B vaccine in the Gambian expanded programme on immunisation.

Because of the high prevalence of hepatitis B virus (HBV) infection in The Gambia, HBV vaccination has been incorporated into the national expanded programme on immunisation. We have assessed the efficacy of the vaccine against HBV infection and chronic carriage by examining 720 3-4-year-old children who had received the vaccine in infancy and 816 who had not received it. The vaccine was 84% (95% CI 78-89%) effective against infection and 94% (84-98%) effective against chronic carriage. Vaccinated infants of mothers positive for hepatitis B surface and e antigens were at greater risk of breakthrough infection and chronic carriage than infants of uninfected mothers. The high vaccine efficacy against the HBV carrier state, the main risk factor for the development of chronic liver disease and liver cancer, offers hope that the prevalence of these diseases may be reduced in the future.

Carrier State↗
PubMed1992

The Gambia Hepatitis Intervention Study: follow-up of a cohort of children vaccinated against hepatitis B.

Hepatitis B vaccine has been introduced into The Gambia's national Expanded Programme on Immunization, with the aim of evaluating the impact on chronic liver diseases and in particular on hepatocellular carcinoma. As part of the project, a cohort of 1000 children was recruited to assess the long-term protection induced by the vaccine. The first 3 years of follow-up are described. By the age of 3 years, 95% of the children had protective antibody levels; 4 (0.6%) are known to be carriers in contrast to the 90-140 that would be expected in the absence of vaccination. The protective effectiveness of vaccine in preventing chronic carriage in the first 3 years of life is thus estimated as 95%. Since the risk of becoming a carrier is highest in those infected early in life, these results are encouraging.

Antigens, Viral↗
PubMed1992

HIV-1 and HIV-2 seroprevalence rates in mother-child pairs living in The Gambia (west Africa).

A seroepidemiological study was conducted, during 1988 and 1989, of mother-child pairs living in The Gambia (West Africa) in order to determine the distribution of the human immunodeficiency viruses type 1 (HIV-1) and type 2 (HIV-2). Specimens were obtained from 931 children (age range, 14-17, months) and 923 mothers (age range, 14-17 years) using village-based cluster samples; the children are participating in The Gambia Hepatitis Intervention Study (GHIS), a large-scale HBV vaccination program. Large numbers of indeterminate Western blot patterns were observed among the mothers, mainly for HIV-1 antibodies; HIV-1 infected subjects were not found, whereas an HIV-2 seroprevalence rate of 0.75% was observed. The children born to the seven HIV-2 positive women were seronegative for HIV-2 antibodies, and none of the children showed HIV-2 or HIV-1 seropositively.

Adolescent↗
PubMed1991

Hepatitis B vaccine in the Gambian Expanded Programme on Immunization: factors influencing antibody response.

Data on over a thousand Gambian children have been analysed to examine factors influencing their antibody levels following immunization with hepatitis B vaccine administered during the first year of life. The dominant effect was the time between the last dose of vaccine and taking the blood sample. There was considerable variation in vaccine response by area of residence which could not be explained by any other factor. The hepatitis B surface antigen (HBsAg) status of the mother and the age at vaccination did not appear to have an effect, but there was some indication that a delay in receiving the second dose of vaccine led to a marginally lower response.

Antibodies, Viral↗
PubMed1991

Response to hepatitis B vaccine in relation to the hepatitis B status of family members.

The influence of the hepatitis B status of family members on the response to hepatitis B vaccine of an infant has been examined in 395 families. The presence of one or more HBsAg-positive family members did not appear to have any effect on the vaccine response. This is an encouraging finding as children born into carrier families are at an increased risk of becoming carriers themselves. That the vaccine response of such children is as good as for those born into non-carrier families means that they are likely to be protected against the carrier state by the vaccine.

Family↗
PubMed1990

Risk factors for transmission of hepatitis B virus to Gambian children.

Risk factors for hepatitis B virus transmission were examined in 973 Gambian children aged 6 months to 5 years. 33% had evidence of infection with hepatitis B virus and a third of these were carriers. A significant association was found between infection and tropical ulcer scars, and between e antigenaemia and the presence of bedbugs in each child's bed. There was no association between infection and traditional scarring, circumcision, or injections. Skin disease and arthropods are the two most likely modes of transmission of hepatitis B virus between children in West Africa.

Acute Disease↗
PubMed1990

Hepatitis B surface antigen reactivity in man due to a new variant of hepatitis B virus.

A new type of hepatitis B virus (HBV) infection has been encountered in Senegalese infants and French adults characterized by serum hepatitis B surface antigen (HBsAg) without antibodies to the core antigen (anti-HBc). As the infection is not associated with the presence of the e antigen, it differs from HBV in its core antigen. After the loss of HBsAg, neither anti-HBc nor antibodies to HBsAg (anti-HBs) become detectable. This new infection (called HBV2 as opposed to the classical HBV1 infection) was found in infants with anti-HBs, either naturally acquired or produced by immunization against HBV. The use of monoclonal anti-HBs antibodies showed that two epitopes of HBV1 surface antigen could be detected in HBV2-positive sera. HBV DNA sequences could only be found in one of 15 HBV2-infected children using a DNA-DNA hybridization procedure; low levels of HBV DNA were also detected in 58% of the HBsAg-positive adult sera tested. If this new infection, apparently related to HBV1, is shown to cause chronic liver disease, hepatitis B vaccine should also contain surface antigen from HBV2.

Adult↗
PubMed1988

[Immunogenicity of a hepatitis B vaccine obtained by genetic recombination and containing products of S and pre-S2 genes].

Immunization against hepatitis B by means of a vaccine obtained by genetic recombination on chinese hamster ovary cells was attempted in 32 adult subjects. The HBs antigen was purified from the culture supernatant and contained S and pre S2 genes products. Three 20 micrograms doses were injected intramuscularly at intervals of one month. Anti-HBs seroconversion levels and the geometrical mean of antibodies were slightly higher than those observed with plasma vaccines or genetically engineered yeast-derived vaccine. Antibodies directed against HBs appeared more rapidly and at a higher titre. Anti-pre S2 antibodies were detected after the third injection in 84 per cent of the subjects vaccinated. This recombinant hepatitis B vaccine prepared from chinese hamster ovary cells will probably be as effective as the first generation vaccines obtained by purifying the HBs antigen obtained from the blood of asymptomatic carriers.

Adult↗
PubMed1987

HBsAG positive reactivity in man not due to hepatitis B virus.

A viral infection characterised by serum HBsAg positivity with serum anti-HBc negativity has been encountered in Senegal. The infection is not associated with the presence of HBeAg, so it differs from hepatitis B virus in its core antigen, but the surface antigen of the two viruses share some epitopes. After the loss of HBsAg, neither anti-HBc nor anti-HBs becomes detectable. Anti-HBs, naturally acquired or produced by immunisation, does not protect against this new infection. Chronic carriage occurs. If this new infection is confirmed to cause chronic liver disease, hepatitis B vaccine should include surface antigen from the new virus.

Carrier State↗
PubMed1987

Age- and sex-related study of hepatitis B virus chronic carrier state in infants from an endemic area (Senegal).

This report concerns hepatitis B virus (HBV) infections observed in 155 infants from Senegal, studied with a view to determining the factors involved in development of the chronic carrier state. A chronic carrier state was observed in 50.3% of the infants. This study confirms that the risk of chronic carriage is linked to age. This risk declines very rapidly with age, falling from 82% in infants under 6 months old, to 15% in children between the ages of 2 and 3 years. Spontaneous elimination of hepatitis B surface antigen (HBsAg) is uncommon in HBsAg carriers during childhood. The difference observed in chronic carriage between males and females is due to a difference in susceptibility of the two sexes to the development of the chronic carrier state: HBV infections (before 2 years of age) lead to a chronic carriage in 77% of males as against 50% of females. These conclusions are important in view of the immunisation programs being carried out against hepatitis B virus in endemic areas. For a maximum efficacy, vaccination must be carried out at birth, or shortly afterwards.

Age Factors↗
PubMed1987

Hepatitis B vaccine in infants from an endemic area: long-term anti-HBs persistence and revaccination.

Persistence of anti-HBs in 156 Senegalese infants immunized with hepatitis B vaccine was studied for periods ranging from 2 to 6 years after booster dose administration. Six years after the booster dose, 90.4% of the infants had detectable anti-HBs antibodies, with 78.1% having titers higher than 10 mIU/ml. The geometric mean titer was 60 mIU/ml. Females showed higher anti-HBs values than males. In a group of 11 infants who received no booster dose, anti-HBs antibodies were detectable 7 years after the first dose. However, the geometric mean titer was lower (26 mIU/ml). Revaccination (56 infants) led to an increase of the geometric mean titer to 469 mIU/ml 2 months later. These results show that a booster injection every 5-6 years should provide adequate protective anti-HBs levels in infants.

Antibodies, Viral↗
PubMed1986

Seven-year study of hepatitis B vaccine efficacy in infants from an endemic area (Senegal).

A booster dose of hepatitis B vaccine was given to 143 children in whom hepatitis B had not developed 1 year after initial vaccination. Over the next six years the incidence of hepatitis B in this group was 1.5% per year compared with 11.5% per year in a similar group of unvaccinated children. In the first 4 years the protective efficacy of the vaccine was 100%, but during the 5th and 6th years it fell to 67%. For maximum protection a second booster is needed, 5 years after the first.

Carrier State↗