Showing papers by "Paul Milligan published in 2012"
TL;DR: The data suggest that seasonal malaria chemoprevention has the potential to avert several million malaria cases and tens of thousands of childhood deaths each year if successfully delivered to the populations at risk.
Abstract: Seasonal malaria chemoprevention, previously known as intermittent preventive treatment in children, is highly effective in areas with a short malaria transmission season. Here we assess seasonality in malaria incidence data and define a predictor of seasonality based on rainfall. We then use spatial rainfall, malaria endemicity and population data to identify areas likely to have highly seasonal malaria incidence, and estimate the population at risk and malaria burden in areas where seasonal malaria chemoprevention would be appropriate. We estimate that in areas suitable for seasonal malaria chemoprevention, there are 39 million children under 5 years of age, who experience 33.7 million malaria episodes and 152,000 childhood deaths from malaria each year. The majority of this burden occurs in the Sahelian or sub-Sahelian regions of Africa. Our data suggest that seasonal malaria chemoprevention has the potential to avert several million malaria cases and tens of thousands of childhood deaths each year if successfully delivered to the populations at risk.
157 citations
TL;DR: Direct and indirect effects of new malaria-control policies, introduced in 2003 and completed during 2006-2008, are likely to have been the key cause of the recent dramatic decrease in child mortality.
Abstract: BACKGROUND: The Demographic Surveillance System established in 1962 in Niakhar Senegal is the oldest in Africa. Here we analyze trends in overall child mortality malaria and other causes of death in Niakhar from the beginning of data collection to 2010. METHODS: After an initial census demographic data were updated yearly from 1963 through 2010. From 1984 causes of death were determined by the verbal autopsy technique. RESULTS: During 1963-2010 infant and under-5 mortality rates decreased from 223 per thousand to 18 per thousand and from 485 per thousand to 41 per thousand respectively. The decrease was progressive during the entire observation period except during 1990-2000 when a plateau and then an increase was observed. Malaria-attributable mortality in under-5 children decreased from 13.5 per thousand deaths per 1000 children per year during 1992-1999 to 2.2 per thousand deaths per 1000 children per year in 2010. During this period all-cause mortality among children aged <5 years decreased by 80%. CONCLUSIONS: Inadequate treatment for chloroquine-resistant malaria and an epidemic of meningitis during the 1990s were the 2 factors that interrupted a continuous decrease in child mortality. Direct and indirect effects of new malaria-control policies introduced in 2003 and completed during 2006-2008 are likely to have been the key cause of the recent dramatic decrease in child mortality.
36 citations
TL;DR: This analysis supports the WHO recommendation for coadministration of IPTi with sulfadoxine-pyrimethamine to infants at the time of the second and third doses of DTP and measles vaccination, in areas of sub-Saharan Africa with moderate to high malaria transmission and where malaria parasites are sensitive to these drugs.
18 citations
TL;DR: The findings show strong support for recent positive selection of both the HbS and HbC alleles and provide insights into how these two alleles have both evolved in the population of northern Ghana.
Abstract: Background
Haemoglobin S (HbS) and C (HbC) are variants of the HBB gene which both protect against malaria. It is not clear, however, how these two alleles have evolved in the West African countries where they co-exist at high frequencies. Here we use haplotypic signatures of selection to investigate the evolutionary history of the malaria-protective alleles HbS and HbC in the Kassena-Nankana District (KND) of Ghana.
16 citations
TL;DR: The proposed model is a combination of the 'all-or-none' and the 'leaky' models, and the summary protective efficacy is a unified measure of the vaccine's twofold effects in completely or partially protecting the vaccinated individuals against the study event.
Abstract: Recurrent event time data are common in experimental and observational studies. The analytic strategy needs to consider three issues: within-subject event dependence, between-subject heterogeneity in event rates, and the possibility of a nonsusceptible fraction. Motivated by the need to estimate the summary protective efficacy from recurrent event time data as seen in many infectious disease clinical trials, we propose a two-part frailty mixture model that simultaneously accommodates all the three issues. In terms of vaccine action models, the proposed model is a combination of the 'all-or-none' and the 'leaky' models, and the summary protective efficacy is a unified measure of the vaccine's twofold effects in completely or partially protecting the vaccinated individuals against the study event. The model parameters of interest are estimated using the expectation-maximization algorithm with their respective variances estimated using Louis's formula for the expectation-maximization algorithm. The summary protective efficacy is estimated by a composite estimand with its variance estimated using the delta method. The performance of the proposed estimation approach is investigated by a simulation study. Data from a trial of malaria prophylaxis conducted in Ghana are reanalyzed.
13 citations
TL;DR: This article examines the properties of the estimator under the additive and multiplicative rate models assumption in which the baseline incidence rate and covariate effects may vary over time and shows analytically and numerically that the estimators gives an appropriate summary measure of the time-varying covariates.
Abstract: Recurrent events data are common in experimental and observational studies. It is often of interest to estimate the effect of an intervention on the incidence rate of the recurrent events. The incidence rate difference is a useful measure of intervention effect. A weighted least squares estimator of the incidence rate difference for recurrent events was recently proposed for an additive rate model in which both the baseline incidence rate and the covariate effects were constant over time. In this article, we relax this model assumption and examine the properties of the estimator under the additive and multiplicative rate models assumption in which the baseline incidence rate and covariate effects may vary over time. We show analytically and numerically that the estimator gives an appropriate summary measure of the time-varying covariate effects. In particular, when the underlying covariate effects are additive and time-varying, the estimator consistently estimates the weighted average of the covariate effects over time. When the underlying covariate effects are multiplicative and time-varying, and if there is only one binary covariate indicating the intervention status, the estimator consistently estimates the weighted average of the underlying incidence rate difference between the intervention and control groups over time. We illustrate the method with data from a randomized vaccine trial.
4 citations