adequately reduce this transmission mechanism, particularly when implementing large-scale programs, is still an open and important empirical question.

We evaluate the impact of two large-scale, government-implemented programs that promote handwashing with soap and improved sanitation in rural Tanzania. The programs are part of a multi-country effort to address poor hygiene and sanitation conditions for large rural populations in the developing world, implemented through local governments with assistance from the World Bank.<sup>4</sup> From mid-2009 to early 2011, the two interventions were rolled out in 10 districts<sup>5</sup> of Tanzania following a factorial experimental design. 181 rural wards included in the study were divided into 4 groups to receive the handwashing intervention alone, the sanitation intervention alone, both the handwashing and sanitation, or neither intervention (control). We conducted an endline survey in 2012, approximately one year after the conclusion of the program. The survey includes 3,619 households and 5,768 children under five, with an effective response rate of 97.8%. The trial was registered as NCT01465204 at clinicaltrial.gov.<sup>6</sup> Handwashing wards were provided with a package of intensive social marketing interventions, including training of community activists, direct consumer contact through road shows, mass media campaigns and promotional activities, and technical assistance to build handwashing stations with local materials. Sanitation wards received a similar package of marketing efforts coupled with a community-led total sanitation triggering event geared towards increasing demand for improved sanitation facilities and promoting open defecation free (ODF) communities, followed by the creation of a village sanitation committee in charge of ensuring sustained behavior change. This was complemented with supply side interventions to train local masons in latrine construction and marketing. In both cases, sanitation marketing messages concentrated on positive aspirational messages rather than shame tactics. No subsidies were used.

Approximately one year after the end of the program, treatment households are significantly more likely to report being exposed to handwashing and sanitation messages of the sort used by the program. Households in sanitation wards are more likely to know of a mason who builds latrines and be aware of a sanitation committee operating in their village. Private latrine construction increased by 12.4 percentage points over the intervention period, a relative increase of 33% compared to the control. Increased latrine coverage leads to a 52% decline (23.1% vs 11.1%) in reported open defecation as the primary means of depositing feces in sanitation wards. Handwashing results are less impressive. Households in handwashing wards show marginal improvements in handwashing with soap prior to food preparation but not at other critical

> 4 Since 2007, the Water and Sanitation Program (WSP) has provided technical assistance to local and national governments implementing large rural sanitation and handwashing promotion programs in India, Indonesia, Peru, Senegal, Tanzania, and Vietnam, under the umbrella of two related projects, Global Scaling Up Handwashing and Global Scaling Up Rural Sanitation. More information is available at www.wsp.org/scalingupsanitation.

> 5 Out of 129 districts in Tanzania at the time of the 2002 census. These districts cover a population of 2,7 million people. 6 http://clinicaltrials.gov/ct2/show/NCT01465204

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