Scaling up insecticide treated net coverage: evidence to support strategic policy decisions and investment
Submitting InstitutionLondon School of Hygiene & Tropical Medicine
Unit of AssessmentPublic Health, Health Services and Primary Care
Summary Impact TypeHealth
Research Subject Area(s)
Medical and Health Sciences: Public Health and Health Services
Summary of the impact
A comprehensive body of research into the effectiveness, cost and
distribution of long-lasting insecticidal nets (LLINs) by LSHTM has made a
major contribution to the reduction of malaria-related mortality between
2008 and 2013, especially among children in Africa. The research formed
the basis of a radically altered strategic approach to combating malaria
by WHO and other agencies, and led to the roll-out of malaria campaigns
based around LLINs in several African countries. LSHTM research into the
technology of LLINs, which also contributed to these developments, is
described in a separate case study.
This case study traces LSHTM contributions to the evidence that justified
the scaling-up of investment and large-scale distribution of
insecticide-treated nets (ITNs) to control malaria. Lead researchers
included Jo Lines, Reader in Malaria Control and Vector Biology, at LSHTM
since 1984 (seconded to WHO 2008-2011); Christian Lengeler, LSHTM Trial
Coordinator and Research Fellow 1992-1995; Peter Smith, Professor of
Tropical Epidemiology, at LSHTM since 1979; Chris Curtis, Professor of
Medical Entomology, at LSHTM from 1976 until his death in 2008; Mark
Rowland, Professor of Medical Entomology, at LSHTM since 2000, and Anne
Mills and Kara Hanson, Professors of Health Economics, at LSHTM since 1979
and 1990. Due to the number of LSHTM researchers contributing to research
into ITNs, work contributing to the technological development of LLINs is
described in a separate case study.
By 1993, the first major field trial of insecticide-treated nets (ITNs)
in Africa (in The Gambia) had shown a remarkably large reduction in
all-cause child mortality. However, to justify large-scale roll-out of
nets, replication across the range of eco-epidemiological conditions in
the region was needed. Lengeler, Smith and country researchers carried out
a series of field trials (in Burkina Faso, Kenya, The Gambia and Ghana)
between 1993 and 1996. The Ghana findings — similar to those in the other
countries — showed a reduction in all-cause child mortality of 17%.3.1
Supporting evidence on cost-effectiveness gathered by Mills and country
economists showed that ITNs were extremely cost-effective.3.2
A subsequent influential 2004 Cochrane review and meta-analysis by
Lengeler concluded that ITN coverage for a cohort of 1,000 children will
on average prevent 5.5 deaths per year across a wide range of
epidemiological settings in rural Africa. Further LSHTM epidemiological
trials conducted between 1995 and 2005 and included in the Cochrane review
confirmed that ITNs are effective against both falciparum and vivax
malaria in regions where the vector mosquito species are different (e.g.
the Amazon Basin and South Asia) but where mortality rates are lower, and
when deployed through other methods of implementation.
Also during 1993 and 1998, small-scale Tanzanian trials by Lines and
Curtis confirmed the entomological mode of action of ITNs, by recording
reductions in sporozoite rates in mosquitoes. This confirmed the
underlying mechanism of the `mass effect',3.3 which occurs when
the insecticide kills so many of the mosquitoes trying to feed through the
net that the transmission capacity of the local mosquito population as a
whole is reduced, protecting the whole community rather than just the
individual sleeper. The researchers argued that in order to obtain the
necessary levels of coverage, nets should be distributed free of charge to
In 2001-2005, LSHTM researchers conducted a series of detailed studies to
examine the role of local commercial markets in delivering mosquito nets
to end users, and showed that the coverage achieved by commercial markets
in nets is more equitable than that achieved by the sale of subsidised
nets by public health systems and projects.3.5 Further work in
2010-2011 demonstrated the epidemiological advantages of free distribution
of nets directly to pregnant women and infants through routine antenatal
and immunisation services.3.6
References to the research
3.1 Binka, FN, Kubaje, A, Adjuik, M, Williams, LA, Lengeler, C, Maude,
GH, Armah, GE, Kajihara, B, Adiamah, JH and Smith, PG (1996) Impact of
permethrin impregnated bednets on child mortality in Kassena-Nankana
district, Ghana: a randomized controlled trial, Tropical Medicine
& International Health, 1(2): 147-154, doi:
10.1111/j.1365-3156.1996.tb00020.x. Citation count: 241.
3.2 Goodman, C, Coleman, P and Mills, A (1999) Cost-effectiveness of
malaria control in sub-Saharan Africa, Lancet, 354(9176): 378-385,
doi: 10.1016/S0140-6736(99)02141-8. Citation count: 138.
3.3 Hill, J, Lines, J and Rowland, M (2006) Insecticide-treated nets, Advances
in Parasitology, 61: 77-128, doi: 10.1016/S0065-308X(05)61003-2.
Citation count: 40.
3.4 Curtis, C, Maxwell, C, Lemnge, M, Kilama, WL, Steketee, RW, Hawley,
WA, Bergevin, Y, Campbell CC, Sachs, J, Teklehaimanot, A, Ochola, S,
Guyatt, H and Snow, RW (2003) Scaling-up coverage with insecticide-treated
nets against malaria in Africa: who should pay?, Lancet Infectious
Diseases, 3(5): 304-307, doi: 10.1016/S1473-3099(03)00612-1.
Citation count: 81.
3.5 Webster, J, Lines, J, Bruce, J, Schellenberg, JRA and Hanson, K
(2005) Which delivery systems reach the poor? A review of equity of
coverage of ever-treated nets, never-treated nets, and immunisation to
reduce child mortality in Africa, Lancet Infectious Diseases,
5(11): 709-717, doi: 10.1016/S1473-3099(05)70269-3. Citation count: 32.
3.6 Okell, LC, Paintain, LS, Webster, J, Hanson, K and Lines, J (2012)
From intervention to impact: modelling the potential mortality impact
achievable by different long-lasting, insecticide-treated net delivery
strategies, Malaria Journal, 11(327), doi:
10.1186/1475-2875-11-327. Citation count: 3.
Mills, Economic Evaluation of National Impregnated Bednet Programme, The
Gambia, WHO-TDR, 1992-1994, $275,000.
Mills, Workshop on Cost-effectiveness Analysis of Impregnated bednets,
WHO-TDR, 1996, $7,500.
Mills, Lines, Hanson, Scaling Up ITN Coverage in Tanzania, Understanding
the Contribution and Limitations of the Private Sector, Gates Malaria
Partnership, 2002-2005, £366,833.
Porter, Lines, Godfrey-Faussett, TARGETS: Team for Applied Research
Generating Effective Tools and Strategies: Proposal for a Research
Programme Consortium in Communicable Diseases, DFID, 1/4/2005-31/3/2010,
Details of the impact
The research carried out by LSHTM has made an important contribution
towards reducing the number of deaths from malaria. Using WHO methods of
estimation, it can be estimated that approximately 1m malaria-related
deaths were prevented by LLINs between 2008 and 2013, mostly among African
children.5.1 This impact was brought about by net distribution
operations and investment decisions during the impact assessment period
(mostly in 2009-2010). The WHO policy that led to these operations, which
explicitly cites LSHTM research as supporting evidence, was first drafted
and announced shortly before the impact assessment period (in 2007).
Nevertheless, it is clear that the operations putting this policy into
practice did take place during the assessment period, and were equally
influenced and justified by the same research, as were the subsequent WHO
statements repeating and amplifying the initial policy announcement.
Following a very limited emphasis on vector control by WHO and leading
agencies in the 1990s, the late 2000s marked a strategic sea change. Since
2006, and supported by the evidence accumulated through the research, WHO
has been recommending ITNs/LLINs as the default vector control
intervention for Africa, with indoor residual spraying (IRS) as a
possible alternative that might be preferable in some settings. The
relevant WHO report, Malaria Vector Control and Personal Protection5.2
acknowledges Curtis' work on the Study Group that produced it, as well as
Rowland's written contribution. It also cites numerous relevant LSHTM
outputs. This document set the scene for further strategic emphasis on
malaria prevention through ITNs/LLINs.
In 2008, The Roll Back Malaria partnership (RBM) — the global framework
for coordinated action against malaria — made ITNs and LLINs the lead
intervention in its Global Malaria Action Plan.5.3 The
plan acknowledges the contributions of no fewer than six LSHTM researchers
and quotes a December 2007 briefing produced by Lines and colleagues for
the Department for International Development (DFID), which was based on
3.1 and 3.3 and itself highlighted LLINs as a central plank in the quest
to eradicate malaria.5.4 As part of the 2008 Global Malaria
Action Plan, `SUFI' (Scaling-Up For Impact) was proclaimed as a goal —
aiming to rapidly reach universal coverage for all populations at risk
with locally appropriate malaria control interventions, with 730m
LLINs to be distributed globally (about 350m in Africa) (5.3, p.
14). The impact paper in Pakistan and the implementation research that
followed led to the LLIN strategy adopted by the Global Fund for South
Asia (e.g. Pakistan and Afghanistan) 5.3 and by WHO for
conflict induced emergencies 5.5.
In 2008, following a series of publications arguing that the impact of
ITNs would be maximised only if they were given free to everyone in the
community (because of the `mass effect' demonstrated by Lines et al.3.3,
3.4), the UN Secretary-General announced a vision of universal
coverage to end malaria deaths.5.6 His message was that
LLINs, along with indoor residual spraying, would be made available to all
people at risk, especially women and children in Africa. It was based on a
WHO position statement on Insecticide-Treated Mosquito Nets which
was first published in 2007 and remained the standard WHO policy position
throughout the 2008-2013 period.5.7 The position statement
explains the reasons for this shift to universal coverage through the use
of ITNs, citing several LSHTM outputs as well as Lengeler's Cochrane
review of the earlier mortality trials. Subsequently, and following these
WHO recommendations, ITN distribution campaigns have mostly been
standalone and designed to provide nets for entire populations, with one
net provided for every two people (eg Uganda). The contributions of LSHTM
research and staff are acknowledged by the WHO unit responsible for global
WHO policy on this topic.5.8
Largely as a result of the strategic initiatives described, expenditure
on malaria control as a whole is expected to exceed $1bn throughout
2008-20135.1, 5.2 with some 40% to 60% of this being spent on
vector control (mostly nets).
Not all countries wish to rely on externally funded and free distribution
of all nets, and some prefer to develop approaches more readily
sustainable over the longer term. LSHTM research findings on the public
health value of commercial markets as a distribution mechanism for
ITNs, and their importance in achieving overall coverage levels,
encouraged several countries to promote a diverse and complementary
mixture of distribution channels. Examples include Kenya, Ghana, Tanzania,
Pakistan and Afghanistan, who are encouraging mixed distribution
systems operating in parallel, including not only mass campaigns but
also distribution of free nets through routine public health systems
(especially antenatal and immunisation services) and unsubsidised
commercial markets.5.9, 5.10
Sources to corroborate the impact
5.1 Number of deaths prevented 2008-13 calculated from: WHO (2012) World
Malaria Report. Geneva: WHO, http://www.who.int/malaria/publications/world_malaria_report_2012/en/
(accessed 14 November 2013) (pp. 59-61); Roll Back Malaria Partnership
(2011) A Decade of Partnership and Results, Progress & Impact
Series, no. 7, September. Geneva: WHO,? http://www.rbm.who.int/ProgressImpactSeries/docs/report8-en.pdf
(accessed 11 November 2013) (pp. 18, 68-69); Roll Back Malaria (2010) World
Malaria Day 2010: Africa Update, Progress & Impact Series, no.
2, April. Geneva: WHO,
(accessed 11 November 2013) (p. 38).
5.2 WHO (2006) Malaria Vector Control and Personal Protection: Report
of a WHO Study Group, WHO Technical Report Series, no. 936, http://whqlibdoc.who.int/trs/WHO_TRS_936_eng.pdf
(accessed 14 November 2013).
5.3 Roll Back Malaria (2008) The Global Malaria Action Plan: For a
Malaria-free World. Geneva: WHO, http://www.rbm.who.int/gmap/gmap.pdf
(accessed 14 November 2013).
5.4 Lines, J, Whitty, CJM and Hanson, K (2007) Prospects for
Eradication and Elimination of Malaria: A Technical Briefing for DFID.
London: DFID Health Resource Centre, http://r4d.dfid.gov.uk/PDF/Outputs/Targets_RPC/HD205-DFID-final-2007-20_2_.pdf
(accessed 14 November 2013).
5.5 WHO (2013) Malaria control in humanitarian emergencies: an
inter-agency field handbook, 2nd edition, WHO, Geneva, http://apps.who.int/iris/bitstream/10665/90556/1/9789241548656_eng.pdf
(accessed 25 November 2013).
5.6 Ki-moon, B (2008) UN Secretary-General's video message on World
Malaria Day — announcing vision for universal coverage to end malaria
deaths, statement, 25 April. New York: UN, http://www.un.org/sg/statements/index.asp?nid=3118
(accessed 14 November 2014).
5.7 WHO (2007) Insecticide-treated Mosquito Nets: a WHO Position
Statement. Geneva: WHO, http://www.who.int/malaria/publications/atoz/itnspospaperfinal/en/index.html
(accessed 14 November 2014) (remains the primary WHO policy document on
5.8 See paragraph 4 of letter from Coordinator of the Vector Control Unit
at the Global Malaria Programme, WHO. Available upon request.
5.9 Njau, RJA, de Savigny, D, Gilson, L, Mwageni, E and Mosha, FW (2009)
Implementation of an insecticide-treated net subsidy scheme under a
public-private partnership for malaria control in Tanzania — challenges in
implementation, Malaria Journal, 8(201), doi:
5.10 Kolaczinski, JH, Muhammad, N, Khan, QS, Jan, Z, Rehman, N, Leslie,
TJ and Rowland, M (2004) Subsidized sales of insecticide-treated nets in
Afghan refugee camps demonstrate the feasibility of a transition from
humanitarian aid towards sustainability, Malaria Journal, 3(15),