Comparative functional survival and equivalent annual cost of 3 long-lasting insecticidal net (LLIN) products in Tanzania: A randomised trial with 3-year follow up

Autoři: Lena M. Lorenz aff001;  John Bradley aff003;  Joshua Yukich aff004;  Dennis J. Massue aff005;  Zawadi Mageni Mboma aff001;  Olivier Pigeon aff010;  Jason Moore aff006;  Albert Kilian aff011;  Jo Lines aff001;  William Kisinza aff005;  Hans J. Overgaard aff012;  Sarah J. Moore aff006
Působiště autorů: Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom aff001;  Queen’s Medical Research Institute, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom aff002;  MRC Tropical Epidemiology Group, London School of Hygiene & Tropical Medicine, London, United Kingdom aff003;  Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America aff004;  National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania aff005;  Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, Tanzania aff006;  Epidemiology and Public Health Department, Swiss Institute of Tropical and Public Health, Basel, Switzerland aff007;  University of Basel, Basel, Switzerland aff008;  Ifakara Health Institute, Dar es Salaam, Tanzania aff009;  Plant Protection Products and Biocides Physico-chemistry and Residues Unit, Agriculture and Natural Environment Department, Walloon Agricultural Research Centre, Gembloux, Belgium aff010;  Tropical Health, Montagut, Spain aff011;  Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway aff012;  Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand aff013
Vyšlo v časopise: Comparative functional survival and equivalent annual cost of 3 long-lasting insecticidal net (LLIN) products in Tanzania: A randomised trial with 3-year follow up. PLoS Med 17(9): e32767. doi:10.1371/journal.pmed.1003248
Kategorie: Research Article
doi: 10.1371/journal.pmed.1003248



Two billion long-lasting insecticidal nets (LLINs) have been procured for malaria control. A functional LLIN is one that is present, is in good physical condition, and remains insecticidal, thereby providing protection against vector-borne diseases through preventing bites and killing disease vectors. The World Health Organization (WHO) prequalifies LLINs that remain adequately insecticidal 3 years after deployment. Therefore, institutional buyers often assume that prequalified LLINs are functionally identical with a 3-year lifespan. We measured the lifespans of 3 LLIN products, and calculated their cost per year of functional life, to demonstrate the economic and public health importance of procuring the most cost-effective LLIN product based on its lifespan.

Methods and findings

A randomised double-blinded trial of 3 pyrethroid LLIN products (10,571 nets in total) was conducted at 3 follow-up points: 10 months (August–October 2014), 22 months (August–October 2015), and 36 months (October–December 2016) among 3,393 households in Tanzania using WHO-recommended methods. Primary outcome was LLIN functional survival (LLIN present and in serviceable condition). Secondary outcomes were (1) bioefficacy and chemical content (residual insecticidal activity) and (2) protective efficacy for volunteers sleeping under the LLINs (bite reduction and mosquitoes killed). Median LLIN functional survival was significantly different between the 3 net products (p = 0.001): 2.0 years (95% CI 1.7–2.3) for Olyset, 2.5 years (95% CI 2.2–2.8) for PermaNet 2.0 (hazard ratio [HR] 0.73 [95% CI 0.64–0.85], p = 0.001), and 2.6 years (95% CI 2.3–2.8) for NetProtect (HR = 0.70 [95% CI 0.62–0.77], p < 0.001). Functional survival was affected by accumulation of holes, leading to users discarding nets. Protective efficacy also significantly differed between products as they aged. Equivalent annual cost varied between US$1.2 (95% CI $1.1–$1.4) and US$1.5 (95% CI $1.3–$1.7), assuming that each net was priced identically at US$3. The 2 longer-lived nets (PermaNet and NetProtect) were 20% cheaper than the shorter-lived product (Olyset). The trial was limited to only the most widely sold LLINs in Tanzania. Functional survival varies by country, so the single country setting is a limitation.


These results suggest that LLIN functional survival is less than 3 years and differs substantially between products, and these differences strongly influence LLIN value for money. LLIN tendering processes should consider local expectations of cost per year of functional life and not unit price. As new LLIN products come on the market, especially those with new insecticides, it will be imperative to monitor their comparative durability to ensure that the most cost-effective products are procured for malaria control.

Klíčová slova:

Blood – Cost-effectiveness analysis – Death rates – Insecticides – Malaria – Mosquitoes – Public and occupational health – Tanzania


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PLOS Medicine

2020 Číslo 9

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