Data management for an efficacy trial of a vaccine in the Gambia.

An individually randomised double-blind trial of PRP-T Hib conjugate vaccine was conducted in the Gambia between 1993 and 1995, in which 42,848 children were randomised into one of 10 groups, five corresponding to vaccine and five to placebo. Basic demographic data were collected on all children, and administration details of all doses of EPI vaccines were recorded. In addition, details on all doses of vaccines were recorded on each child's home-based health card; 2,681 episodes of possible Hib disease were investigated and for each episode detailed clinical data were collected. These investigations yielded 50 cases of confirmed Hib disease, which formed the basis of the final efficacy results. In all 50 cases, the data on the children's health card, describing the doses of study vaccine received exactly, matched the vaccination database which was filled with data returned from the clinics. The data-management procedures are described in detail in this paper.

Rate of decline of percentage CD4+ cells is faster in HIV-1 than in HIV-2 infection.

Increasing evidence suggests that the pathogenesis of HIV-1 is different from that of HIV-2. Thus, we have measured, longitudinally at various times over a median follow-up of 2.1 years, the percentage CD4+ cells of 94 patients infected with HIV-1 and 164 patients infected with HIV-2. The pattern of decline of CD4% over time was linear for patients with either infection. Multilevel statistical modeling techniques showed that after stratifying for HIV status, the rate of decline of CD4% was faster among patients who died than among those who survived (difference in rate of decline = 2.34% CD4+ cells/year; p = 0.0002). After stratifying for survival status, the rate of decline was faster and less variable among patients infected with HIV-1 than among patients infected with HIV-2 (difference in rate of decline = 1.12% CD4+ cells/year; p = 0.05). The proportion of patients who showed no fall in CD4+ cells was higher in HIV-2 than in HIV-1 infection (p = 0.026). These data suggest fundamental differences between the two infections, with HIV-1 being more pathogenic resulting in a faster and more homogeneous rate of decline than HIV-2. In HIV-2 infection, disease in many patients progresses slowly, but in some the advance is just as fast as that in HIV-1 infection. The reasons for this marked heterogeneity need elucidation to understand the disease and to target therapeutic interventions against HIV-2 in those most at risk.

Malaria in a peri-urban area of The Gambia.

A clinical and entomological survey of malaria was carried out in Bakau, a peri-urban coastal settlement in The Gambia, from June 1988-May 1989. Only 41 of a cohort of 560 children, aged from three months to nine-years-old, experienced a clinical episode of malaria during the observation period. The majority of cases were identified at clinics and not by regular community surveillance. In Bakau Old Town episodes of malaria were more common on the periphery of the settlement, adjacent to typical anopheline breeding sites, than in the centre. Overall malaria cases were not significantly clustered in space and time, although three pairs of cases among children sleeping in the same room at the same time were identified. A cross-sectional survey in November, at the end of the rainy season, revealed a point prevalence parasitaemia of 2.0% and a spleen rate of 0.3%. All malariometric parameters measured were much lower than any found in comparable studies undertaken in rural areas of the country, reflecting the low number of malaria vectors, Anopheles gambiae complex mosquitoes, found in Bakau. Chloroquine consumption, sleeping under bednets, houses with ceilings, the use of insecticide aerosols and burning traditional mosquito repellents may all have contributed to the low prevalence of malaria in the study area.