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Estimating intervention effectiveness in trials of malaria interventions with contamination

Multerer, Lea; Vanobberghen, Fiona; Glass, Tracy R.; Hiscox, Alexandra; Lindsay, Steven W.; Takken, Willem; Tiono, Alfred; Smith, Thomas

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Lea Multerer

Fiona Vanobberghen

Tracy R. Glass

Alexandra Hiscox

Willem Takken

Alfred Tiono

Thomas Smith


Background: In cluster randomized trials (CRTs) or stepped wedge cluster randomized trials (SWCRTs) of malaria interventions, mosquito movement leads to contamination between trial arms unless bufer zones separate the clusters. Contamination can be accounted for in the analysis, yielding an estimate of the contamination range, the distance over which contamination measurably biases the efectiveness. Methods: A previously described analysis for CRTs is extended to SWCRTs and estimates of efectiveness are provided as a function of intervention coverage. The methods are applied to two SWCRTs of malaria interventions, the SolarMal trial on the impact of mass trapping of mosquitoes with odor-baited traps and the AvecNet trial on the efect of adding pyriproxyfen to long-lasting insecticidal nets. Results: For the SolarMal trial, the contamination range was estimated to be 146 m (95% credible interval [0.052, 0.923] km), together with a 31.9% (95% credible interval [15.3, 45.8]%) reduction of Plasmodium infection, compared to the 30.0% reduction estimated without accounting for contamination. The estimated efectiveness had an approximately linear relationship with coverage. For the AvecNet trial, estimated contamination efects were minimal, with insufcient data from the cluster boundary regions to estimate the efectiveness as a function of coverage. Conclusions: The contamination range in these trials of malaria interventions is much less than the distances Anopheles mosquitoes can fy. An appropriate analysis makes bufer zones unnecessary, enabling the design of more cost-efcient trials. Estimation of the contamination range requires information from the cluster boundary regions and trials should be designed to collect this.


Multerer, L., Vanobberghen, F., Glass, T. R., Hiscox, A., Lindsay, S. W., Takken, W., …Smith, T. (2021). Estimating intervention effectiveness in trials of malaria interventions with contamination. Malaria Journal, 20(1), Article 413.

Journal Article Type Article
Acceptance Date Sep 21, 2021
Online Publication Date Oct 20, 2021
Publication Date 2021
Deposit Date Nov 9, 2021
Publicly Available Date Dec 16, 2021
Journal Malaria Journal
Publisher BioMed Central
Peer Reviewed Peer Reviewed
Volume 20
Issue 1
Article Number 413


Published Journal Article (1.4 Mb)

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Copyright Statement
© The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which<br /> permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the<br /> original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or<br /> other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line<br /> to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory<br /> regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this<br /> licence, visit The Creative Commons Public Domain Dedication waiver (http://creativeco<br /> applies to the data made available in this article, unless otherwise stated in a credit line to the data.

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