The Effect of Malaria Transmission Intensity on Neonatal Mortality in Endemic Areas

Tediosi

The American Journal of Tropical Medicine and Hygiene

et al. 2006

Self Cite

Abstract. We predict the effects of introduction of a pre-erythrocytic vaccine against Plasmodium falciparum into a malaria-endemic population in Africa. We use a stochastic simulation model that includes components of transmission, parasitology, and clinical epidemiology of malaria and was validated using the results of field trials of the RTS,S/AS02A vaccine. The results suggest that vaccines with efficacy similar to that of RTS,S/AS02A have a substantial impact on malaria morbidity and mortality during the first decade after their introduction, but have negligible effects on malaria transmission at levels of endemicity typical for sub-Saharan Africa. The main benefits result from prevention of morbidity and mortality in the first years of life. Vaccines with very short half-life or low efficacy may have little overall effect on incidence of severe malaria. A similar approach can be used to make predictions for other strategies for deployment of the vaccine and to other types of malaria vaccines and interventions.

Section: Methodsmentioning

confidence: 99%

Predictions of the Epidemiologic Impact of Introducing a Pre-Erythrocytic Vaccine Into the Expanded Program on Immunization in Sub-Saharan Africa

Tediosi

The American Journal of Tropical Medicine and Hygiene

et al. 2006

Self Cite

“…The model we use to predict the incidence of such deaths is considered in an accompanying paper. 24 D 2 comprises post-neonatal indirect mortality that is provoked by an acute attack of malaria, which together with other co-morbidity or enhanced susceptibility, leads to subsequent death.…”

Section: Modelmentioning

confidence: 99%

An Epidemiologic Model of Severe Morbidity and Mortality Caused by Plasmodium Falciparum

The American Journal of Tropical Medicine and Hygiene

Molineaux

et al. 2006

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146

Abstract. The intensity of Plasmodium falciparum transmission has multifarious and sometimes counter-intuitive effects on age-specific rates of severe morbidity and mortality in endemic areas. This has led to conflicting speculations about the likely impact of malaria control interventions. We propose a quantitative framework to reconcile the various apparently contradictory observations relating morbidity and mortality rates to malaria transmission. Our model considers two sub-categories of severe malaria episodes. These comprise episodes with extremely high parasite densities in hosts with little previous exposure, and acute malaria episodes accompanied by co-morbidity or other risk factors enhancing susceptibility. In addition to direct malaria mortality from severe malaria episodes, the model also considers the enhanced risk of indirect mortality following acute episodes accompanied by co-morbidity after the parasites have been cleared. We fit this model to summaries of field data from endemic areas of Africa, and show that it can account for the observed age-and exposure-specific patterns of pediatric severe malaria and malaria-associated mortality in children. This model will allow us to make predictions of the long-term impact of potential malaria interventions. Predictions for children will be more reliable than those for older people because there is a paucity of epidemiologic studies of adults and adolescents.

“…If transmission is frequent, then all mothers will have similar immune status. 22 We parameterize the multiplication factor that models the effect of maternal immunity D m with a decay function that lies between 0 (maximal effect, corresponding to the status at birth), and 1 (no reduction in density), such that…”

Section: E(ln(y(ij)))mentioning

confidence: 99%

A Model for Natural Immunity to Asexual Blood Stages of Plasmodium Falciparum Malaria in Endemic Areas

Smith

The American Journal of Tropical Medicine and Hygiene

et al. 2006

Self Cite

164

Abstract. Most mathematical models for acquired immunity to Plasmodium falciparum consider effects of immunity on duration of infection and infectiousness, but do not consider the most evident effect of immunity, which is to reduce parasite densities. Few attempts have been made to fit such models to field data. We propose a stochastic simulation model to predict the distributions of P. falciparum parasite densities in endemic areas, in which acquired immunity acts by reducing parasite densities. We have fitted this model to age-specific prevalence and geometric mean densities from settings in Ghana, Nigeria, and Tanzania. The model appears to reproduce reasonably well the parasitologic patterns seen in malariologic surveys in endemic areas and is appropriate for predicting the impact of interventions such as vaccination in the context of continual exposure to P. falciparum.