13% among those living in solid houses (column 8), compared to the control. Again, we do not find impacts on respondents living in non/semi-solid dwellings (column 7). We also explicitly asked about malaria cases and testing behaviors. However, Annex Table D9 shows no significant impact of the ads on these outcomes. The general lack of effect on fever and malaria incidence throughout the campaign period can be attributed to the necessity of maintaining protective actions (such as consistently using bed nets) over an extended duration for them to yield health benefits. This justifies our decision to enlist a fresh cohort of respondents and gather data on malaria incidence after the campaign concluded.

# **5.2.2 Self-reported malaria incidence after the campaign**

Table 4 shows the impact on malaria incidence in the household since the launch of the campaign in August 2020, self-reported in the cross-sectional survey conducted 1-3 months after the end of the campaign. The table reports incidence both at the extensive (if any household member had malaria, columns 1-4) and intensive margins (share of household members who had malaria, columns 5-8). In both cases, the estimates suggest null impact of the ads on overall malaria incidence (columns 1-2 and 5-6). Yet, columns (3-4) and (7-8) unmask substantial heterogeneity in ad effectiveness, showing a significant effect on households living in solid dwellings. For them, the ad campaign reduced the probability that any member reported malaria by 2.4 p.p., a 44% reduction compared to control and, consequently, lowered the share of infected members by 0.8 p.p., a 53% decrease.

Figure 4 provides evidence about the role of bed net ownership on moderating the effectiveness of advertisements. The left panel shows that the reduction in malaria cases is more substantial and statistically significant for households living in solid dwellings equipped with at least one bed net. The right panel shows that among households with bed nets, the decrease is greater for those that have at least one bed net for every two members. This suggests that a minimum number of bed nets per member is necessary for the ad campaign to affect outcomes significantly. Finally, the figure also confirms the absence of any effects among non-solid dwellers, for which the coefficient estimates are not significant and point towards the opposite direction.

Table D10 displays results concerning bed net ownership and the reapplication of insecticide to existing ones. There is no indication that the campaign influenced the likelihood of individuals owning a bed net (columns 1-3), or their inclination to purchase one among those who did not already own one (columns 4-6).<sup>34</sup> On the other hand, the ad campaign increased the likelihood by 6.7 p.p. (or 17%) that bed net owners in solid dwellings re-treated their mosquito nets with insecticide (columns 7-9 of Annex Table D10). While the ads did not explicitly suggest this action, they probably reminded people about the importance of insecticide treatment to repel mosquitoes and enhance the effectiveness of bed nets.

Finally, Annex Tables D11 presents impacts on individuals’ concerns about getting malaria in the next year, respectively. Among respondents living in solid dwellings and with no mosquito nets

> 34This finding is also in line with the content of the campaign, which was not explicitly trying to persuade individuals to purchase bed nets.

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