is pivotal to ensure that a high share of the population is willing to get vaccinated. In addition, we show that simple messages, of a kind that could be easily disseminated, about the relative safety of COVID-19 vaccines can substantially increase people’s stated willingness to be vaccinated. We also show that local health workers have a crucial role in building this trust. In addition, our findings point to existing explanations for vaccine hesitancy that should potentially receive less attention. Most notably, we show it is unlikely that misinformation on social media is the key driver of vaccine hesitancy in PNG. Furthermore, our results illustrate that people’s concerns about COVID-19 and their history of vaccination is unrelated to their willingness to receive a vaccine for COVID-19. Collectively, these findings suggest communication campaigns should recognize the distinct nature of the hesitancy people have around COVID-19 vaccines and greater efforts should be made to communicate that getting vaccinated is the single best way to prevent severe illness or death from COVID-19.

We make two notable contributions to the existing literature on vaccine hesitancy in this paper. Firstly, we are among the first to conduct a detailed examination of people’s hesitancy regarding COVID-19 vaccines using both causal and descriptive evidence in a low- and middle-income country. Existing studies in these settings typically do not go beyond reporting on the level of willingness to receive the COVID-19 vaccine and the main reasons respondents state for their hesitancy about getting vaccinated (Africa CDC, 2021; Solís Arce et al., 2021). We provide new insights by clearly identifying the most plausible drivers of hesitancy regarding the COVID-19 vaccine and testing the elasticity of people’s willingness to get vaccinated to different messages. The combination of these descriptive and experimental findings helps shed light on both the issues likely to be reducing demand for COVID-19 vaccines and the degree to which it is possible to increase demand through communication campaigns.

Secondly, by closely aligning the design and implementation of broadly representative phone surveys with an online randomized survey experiment, we provide additional insights about the generalizability of the findings. Prior work on COVID-19 vaccine hesitancy has tended to involve either observational data from phone surveys (Solís Arce et al., 2021) or online experiments (Palm et al., 2021) in isolation. In contrast, we asked the same questions to the more broadly representative phone survey samples of respondents as were asked to participants in the online randomized survey experiment. By comparing the results of these different survey techniques we were able to better estimate the effects of the treatments on a broader share of the population. Furthermore, the similarities in descriptive results across the distinct approaches illustrate the robustness of our general findings.

This paper is structured as follows. In the next section we review the related literature about vaccine hesitancy. This is followed by an overview of the setting and methodology used. We then present the results of the representative phone survey and online randomized survey experiment separately, as well as analysis that draws on both. We conclude with a discussion of the implications of our findings.

# **2. Related Literature**

Existing work on vaccine hesitancy comes in two forms. In the first, observational studies are used either to simply quantify levels of vaccine hesitancy or to identify beliefs and traits associated with negative perceptions of vaccination. The second body of literature involves either inference from observational studies or experimental evidence used for the sake of understanding the causes of vaccine hesitancy and learning about means of reducing it. Almost all the published studies in both sets of literature come from prior to the COVID-19 pandemic. The vast majority of available work is from developed countries (Dubé et al., 2015; Solís Arce et al., 2021).

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