The protective effectiveness of control interventions for malaria prevention: a systematic review of the literature

Abstract

Background: Thanks to a considerable increase in funding, malaria control interventions (MCI) whose efficacy had been demonstrated by controlled trials have been largely scaled up during the last decade. Nevertheless, it was not systematically investigated whether this efficacy had been preserved once deployed on the field. Therefore, we sought the literature to assess the disparities between efficacy and effectiveness and the effort to measure the protective effectiveness (PE) of MCI. Methods: The PubMed database was searched for references with keywords related to malaria, to control interventions for prevention and to study designs that allow for the measure of the PE against parasitemia or against clinical outcomes. Results: Our search retrieved 1423 references, and 162 articles were included in the review. Publications were scarce before the year 2000 but dramatically increased afterwards. Bed nets was the MCI most studied (82.1%). The study design most used was a cross-sectional study (65.4%). Two thirds (67.3%) were conducted at the district level or below, and the majority (56.8%) included only children even if the MCI didn’t target only children. Not all studies demonstrated a significant PE from exposure to MCI: 60.6% of studies evaluating bed nets, 50.0% of those evaluating indoor residual spraying, and 4/8 showed an added PE of using both interventions as compared with one only; this proportion was 62.5% for intermittent preventive treatment of pregnant women, and 20.0% for domestic use of insecticides. Conclusions: This review identified numerous local findings of low, non-significant PE –or even the absence of a protective effect provided by these MCIs. The identification of such failures in the effectiveness of MCIs advocates for the investigation of the causes of the problem found. Ideal evaluations of the PE of MCIs should incorporate both a large representativeness and an evaluation of the PE stratified by subpopulations.

Accounting for regional transmission variability and the impact of malaria control interventions in Ghana: A population level mathematical modelling approach

“…Impact of increasing the universal coverage levels of ITNs/LLINs were tested with selected scenarios for the various zones. Results obtained from the models after simulation shows that, achieving elevated levels of LLIN coverage of 70.0% and 90.0% respectively, given usage at baseline, level of protective e cacy of LLINs at 40.0% and IRS at 30.0% [37], while keeping the coverage levels of IRS at baseline at 2018, leads to a 2.5% and 8.9% reduction in uncomplicated cases in the Guinea savannah, 8.2 % and 17.3% in the Transitional forest and 9.9 % and 19.8% in the Coastal savannah respectively, S2 Fig 1. For predictions of all reported clinical incidence of malaria (uncomplicated and severe), the corresponding reductions in the incidence rates for all the zones are shown on Table 2. For IRS only, uncomplicated cases averted, as shown in Fig 6 and S2 Figs 2, was 78.5% versus 80.9% for a 90.0% IRS coverage with a 30.0% and 60.0% levels of PE respectively for by 2030.…”

Estimating the Risk of Declining Funding for Malaria in Ghana: The case for continued investment in the malaria response

“…It must be noted that studies have shown that LLIN use varies considerably by urbanization and socioeconomic status with low net use being recorded among higher income households in urban areas [25]. Given that the only data available were national averages, it is likely that the impact of net use is overestimated if indeed, use is high amongst the population at risk in rural areas but low amongst those living in low-risk urban areas.…”

Malaria Control and Infant Mortality in Africa

“…Researchers have therefore also studied the effectiveness of malaria control interventions, in particular the impact of ITN distributions in real-life, at scale conditions. A meta-analysis by Kesteman et al (2017) provides a recent systematic overview of this literature. They document a surge in the number of publications since 2009, reflecting the growing general interest in this question.…”

“…In this article, we contribute to evaluating the effectiveness of recent malaria control interventions by improving the methodology in terms of external and internal validity. Kesteman et al (2017) conclude their literature review by the following recommendations for future research: "sample all geographical and/or cultural patterns, stratify the evaluation [...], adjust for socio-demographic variables that are associated with the outcomes". In a special issue of the American Journal of Tropical Medicine and Hygiene dedicated to this topic, Yazoume et al (2017) come to the same conclusion.…”

“…Whether these conditions hold for at-scale interventions is an open question of interest. Over 150 local longitudinal or cross-sectional studies have been published in recent years by medical journals to assess the effectiveness of control efforts on malaria prevalence, and 38% find no significant results (Kesteman et al, 2017). Among those few studies that looked at infant mortality as well, both zero, small and large effects were found.…”