childbearing age protects newborn babies against tetanus, our study is relevant for child health and policy.

> 11“Scared straight” originally referred to a program intended to deter juveniles from future crimes by showing them the severity of life in prison to emphasize the consequence of bad behaviors (Petrosino et al., 2014). We call a message that emphasizes the severity of a disease “scared straight,” because the purpose of this message is to emphasize the consequence of non-vaccination, “bad behavior.”

> 12Our finding is consistent with some recent works on framing and fear appeals in developed countries; Nyhan et al. (2014), for example, show that priming alters perceptions, but not behaviors.

> 13Heart rate has been used in psychology literature to evaluate whether fear appeals induce fear because increased heart rate is considered an index for cognitive resources allocated to stimulus (for example, see Ordonana et al, 2009).

> 14Two dollars is equivalent to about two days’ earnings per person, and a little more than the average transportation costs (both ways) for a clinic visit among those in our sample who needed to pay for transportation.

> 15Incentivizing people to induce a desirable behavior has been studied in detail. In developed countries, Sutherland et al. (2010) review the effects of cash incentives on vaccination rates, concluding that cash incentives are effective in promoting vaccine take-ups. Weaver (2014), for example, shows that cash incentives of 10 euros increase vaccine take-up by 27 percentage points. In developing countries, on the other hand, many studies find that effects of cash incentives on vaccination are small and limited (see for example, Robertson et al., 2013; Barham and Maluccio, 2009; Salinas-Rodrguez and Manrique-Espinoza, 2013).

> 16Their study boosts vaccine take-ups also through supply-side intervention by establishing an immunization camp in each village. Our study too reduces the supply-side constraints by ensuring sufficient vaccine stock as discussed below.

17The mean daily earnings per household for the sample was approximately 1,000 naira (144 naira per person), and the mean transportation cost to the nearby health clinic was about 250 naira both ways among those who needed to pay for the transportation (50 percent of the sample).

> 18The purpose of providing the positive but the minimum amount of cash to the control group was to track respondents who visited clinics by using the voucher with the amount of cash incentives indicated.

> 19The “scared straight” flipchart contains 15 slides in total, and 7 out of 15 show pictures of various tetanus patients to repeatedly emphasize the severity of tetanus symptoms. The remaining 8 slides provide information about the symptoms of tetanus (severe pain and muscle spasms) and the effectiveness of the tetanus toxoid vaccination, written in the local language, Hausa. The control flipchart contains only the latter 8 slides with written information and without any images of tetanus patients. Examples of flipcharts are shown in Appendix S1. The difference between the two types of flipcharts was intended to capture the effect of the priming about

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