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.

Keywords: case-control studies; health surveys; indoor residual spraying; insecticide-treated bed nets; intermittent preventive treatment; malaria; prevention and control; protective effectiveness.

Figure 1.. Proportions of CIMPs investigated in the 162 studies included in the review, and the proportions of study designs used.

Figure 2.. Number of references by year of publication, and the proportion of studies whose aim was the measure of the effectiveness of CIMP.

The last year is truncated since the search was performed in June 2015.

Figure 3.. Proportions of study designs and outcomes investigated for the evaluation of PE of bed nets.

Figure 4.. Forest plot of evaluations of PE of bed nets against infection.

Results without CI are not displayed. Box size is proportional to the sample size.

Figure 5.. Forest plot of evaluations of PE of bed nets against other outcomes than infection.

Results without CI are not displayed. Box size is proportional to the sample size.

Figure 6.. Forest plot of evaluations of PE of IRS.

Box size is proportional to the sample size. Recent spraying: ≤6 months before the survey or delay since last IRS round in months.

Figure 7.. Forest plot of evaluations of PE of IPTp.

Box size is proportional to the sample size.

Figure 8.. Forest plot of evaluations of PE of domestic use of insecticides.

Box size is proportional to the sample size.