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Biomedical subjects

S Obaro

Publications and source records attributed to S Obaro.

16 recordsLinked to original sources
PubMed2000

Immunologic memory 5 years after meningococcal A/C conjugate vaccination in infancy.

Infant vaccination with meningococcal conjugates may provide long-term protection against disease. Antibody levels and immunologic memory were assessed in 5-year-old Gambian children who received meningococcal A/C conjugate vaccination (MenA/C) in infancy. At 2 years, they were randomized to receive a booster of MenA/C (conjugate group), meningococcal A/C polysaccharide (MPS group), or inactivated polio vaccine (IPV group). All groups were revaccinated with 10 microg MPS at 5 years of age, as were 39 previously unvaccinated age-matched control subjects. Before revaccination, titers were higher in the conjugate and MPS groups than in control subjects (P<.001); titers for the IPV group were similar to those for control subjects. Ten days after revaccination, the conjugate and IPV groups had similar serogroup C serum bactericidal antibody titers (3421 vs. 2790, respectively). These levels were significantly higher than those in the MPS (426) and control (485) groups (P<.001). Thus, immunologic memory was sustained for > or =5 years; however, MPS challenge at 2 years interfered with a subsequent memory response.

Adult↗
PubMed2000

Salivary antibody response to vaccination with meningococcal A/C polysaccharide vaccine in previously vaccinated and unvaccinated Gambian children.

Development of salivary antibodies at the age of 4 or 5 years to group A and C meningococcal polysaccharides (MenA/C PS) was studied among Gambian children, who had received MenA/C conjugate or PS vaccine in infancy. There was also a control group of 64 age matched children. IgG, IgA, and secretory Ig concentrations were measured by enzyme immuno assay. MenA/C PS vaccine induced antibodies both in previously vaccinated and unvaccinated children. The previous vaccination had not induced long lasting IgA-mediated memory. IgA antibodies were secretory, and most of IgG was serum derived. The IgG salivary response seen was similar to the serum response.

Antibodies, Bacterial↗
PubMed2000

Carriage of serogroup W-135, ET-37 meningococci in The Gambia: implications for immunisation policy?

We found high levels of symptomless carriage of a hyperinvasive Neisseria meningitidis strain (electrophoretic type 37 [ET-37], serogroup W-135) during a vaccine trial in Gambian children in 1996. Serogroup C, ET-37 complex meningococci cause 30-40% of meningococcal disease in countries such as the UK, and have a point prevalence of 0.5-1.0%. The recent Haj-associated spread of serogroup W-135, ET-37 complex meningococci, which has been accompanied by numerous secondary cases, might be explained by the apparently raised carriage rates reported here.

Bacterial Vaccines↗
PubMed2000

A prospective evaluation of a clinical algorithm for the diagnosis of malaria in Gambian children.

Diagnosis of clinical malaria remains difficult, especially in areas where a high proportion of the asymptomatic population have parasitaemia, for the symptoms and signs of malaria overlap with those of other common childhood diseases, such as acute lower respiratory tract infections. However, a study of symptoms and signs in a group of children who presented to Farafenni Health Centre, The Gambia with a history of recent fever identified a group of signs and symptoms which were strong predictors of malaria as opposed to other febrile illnesses. Using these predictors, an algorithm was developed which could be used by fieldworkers and which had a similar sensitivity and specificity for the diagnosis of malaria as that of an experienced paediatrician working without laboratory support. This algorithm has been validated prospectively on 518 children who presented to the Medical Research Council clinic at Basse, The Gambia with fever or a history of recent fever during a 10-month period. A fieldworker obtained a detailed history from the parent or guardian of each child and performed a clinical examination which included measurement of axillary temperature and respiratory rate. Packed cell volume was measured and a thick smear was examined for malaria parasites. A malaria score, based on the presence or absence of malaria-related signs and symptoms, was determined for 382 children who were seen at the clinic during the high transmission season. Using the cut-off score which was optimal during the previous retrospective study, a sensitivity of 70% and a specificity of 77% for a diagnosis of malaria was obtained. The optimal cut-off score for the Basse population was a score of 7; this gave a sensitivity of 88% and a specificity of 62%, figures comparable to those obtained by an experienced paediatrician without laboratory support.

Algorithms↗
PubMed1999

Preparation for a pneumococcal vaccine trial in The Gambia: individual or community randomisation?

In preparation for a large phase-3 trial of pneumococcal polysaccharide/conjugate vaccine among infants in The Gambia, the relative merits of community and individual randomisation were considered. The impact of vaccination might be enhanced in a community randomised trial if there was a substantial 'herd' effect. This might occur if those vaccinated comprise a substantial proportion of potential transmitters of infection. However, there are few data on the sources of pneumococcal infections in The Gambia and with the high degree of mobility of people in The Gambia, it seems unlikely that any herd effect would be strong. In the absence of a herd effect, a community-randomised trial would have lower power for the mortality end-points compared to an individually randomised trial of the same size. In addition, a community-randomised trial might not provide sufficient control against potential confounders and blinding might be difficult to sustain if the vaccine has a strong effect. An individually randomised trial seems a better strategy under the conditions prevailing in The Gambia.

Bacterial Vaccines↗
PubMed1999

Immune response to revaccination with meningococcal A and C polysaccharides in Gambian children following repeated immunisation during early childhood.

Forty-two Gambian children randomised to receive two doses of meningococcal A/C polysaccharide vaccine (MPS) in infancy and either MPS (n = 15), meningococcal A/C conjugate (n = 13) or inactivated polio vaccine (IPV n = 14) at 2 years, were revaccinated with MPS at 5 years of age along with 39 matched control children. Meningococcal A and C polysaccharide antibodies were analysed by ELISA and bactericidal assay (SBA) in sera taken before and 10 days after revaccination. The geometric mean group SBA titre in the MPS group following revaccination was about half that of the unvaccinated controls (0.51 95%CI: 0.28, 0.90) for group A and less than half that of the controls for group C (0.41, 95%CI: 0.16, 1.03 P = 0.06). The group C SBA response in the conjugate group was 14-fold higher than in the MPS group (P < 0.001). Multiple doses of meningococcal polysaccharide in childhood may therefore attenuate the SBA response to both group A and group C polysaccharides. In contrast, vaccination with meningococcal A/C conjugate after MPS in infancy gives immunological memory to N. meningitidis group C.

Antibodies, Bacterial↗
PubMed1998

A randomized controlled trial of artemether/benflumetol, a new antimalarial and pyrimethamine/sulfadoxine in the treatment of uncomplicated falciparum malaria in African children.

We report here the results of a randomized double blind trial comparing coartemether (CGP56697), a combination of artemether and benflumetol, with pyrimethamine/sulfadoxine (P/S). Two hundred eighty-seven children 1-5 years of age with uncomplicated falciparum malaria were enrolled at two centers in The Gambia between July 1996 and December 1996. Following treatment, children were visited at home every 24 hr until a blood film free of asexual parasites was obtained. Genotyping of parasites was used to distinguish recrudescence from new infections. Three days after the start of treatment, 133 (100%) of the CGP56697-treated children compared with 128 (93.4%) of children treated with P/S had cleared their parasites (P = 0.003). The day 15 cure rate was 93.3% for CGP56697 and 97.7% for P/S (P = 0.13). Within the third and fourth week after initiation of therapy, 20 children treated with CGP56697 and one of the P/S-treated children returned with second malaria episodes (P < 0.0001). Genotyping suggested that the majority (19 of 23 [82.6%]) of these second episodes were due to new infections, supporting the World Health Organization recommendation that longer follow-up is not relevant for the assessment of drug efficacy. At the two-week follow-up, 28.9% of the P/S treated children but none of the CGP56697-treated children carried gametocytes (P < 0.0001). This study showed that CGP56697 is safe in African children with acute uncomplicated falciparum malaria, clears parasites more rapidly than P/S, and results in fewer gametocyte carriers. More frequent new infections within the third and fourth week following treatment with CGP56697 than treatment with P/S are likely to be due to the short prophylactic effect of CGP56697.

Antimalarials↗
PubMed1997

Changes in the pattern of infant and childhood mortality in upper river division, The Gambia, from 1989 to 1993.

A surveillance system was used to detect births and deaths in children in a large, rural, West African population from 1989 to 1993. Cause of death was investigated using post-mortem questionnaires. Overall infant (age 0-11 months) and child (age 1-4 years) mortality rates of 80.1 and 18.8 per 1000 per year were recorded. These were reasonably consistent over the period of surveillance. The most frequent cause of death in infants was acute respiratory infection (ARI), whereas in children it was malaria: these two conditions accounted for 41% of the deaths in children under 5 years old. Other leading causes of death were acute gastroenteritis, malnutrition, and septicaemia. Deaths attributed to ARI decreased over the 5-year period, but mortality rates from other causes were either unchanged or increased slightly. Mortality from all causes peaked in the rainy season and was slightly higher in villages which were part of a primary health care programme than in those which were not. There were also no differences between male and female mortality rates beyond one year of age. Despite the introduction of a number of health interventions, there has been no major change in the overall pattern of mortality in children in a rural area of The Gambia. Malaria and ARI remain the main causes of death.

Acute Disease↗