with vaccination (that is, rare negative side effects) are worth taking given the preventive health benefits from the vaccine (that is, minimizing the risk of severe illness and death from COVID-19). We have shown that, consistent with this model, information can raise trust in vaccines in some instances. The instances may, potentially, be quite specific – PNG is a low-income country, where COVID-19 vaccinations are not yet common. Nevertheless, our findings will serve as important starting point for research engaging with vaccine hesitancy elsewhere in the developing world, as countries try to quickly increase vaccination rates.

# <u>6.4 Issues for further research</u>

There is scope to build on our findings. One obvious fruitful area for future research will be expanding our approach to other developing countries. As we noted in the literature review, one salient fact emerging from existing descriptive studies on attitudes to COVID-19 vaccination, is just how much variation there is in vaccine hesitancy between countries (Africa CDC, 2021; Solís Arce et al., 2021). Given such variation, it may be the case that the sources of vaccine hesitancy, and the best means of overcoming it, may vary from country to country. In more authoritarian states, for example, it could be the case that government health workers are not as well trusted. Given potential variation between developing countries, we encourage further research, particularly experimental research elsewhere.

There is also scope to test the effectiveness of different messages delivered using different media. We have shown clearly that information provided via the internet can help shift people’s views on COVID-19 vaccinations. This is an important starting point. Yet, in a country like Papua New Guinea, where the bulk of the population do not currently have access to social media, the main task of increasing people’s willingness to be vaccinated will fall to individuals delivering information in person. Health workers, both because of the nature of their job, and the high levels of trust revealed in the phone survey, will be excellent candidates to deliver information on vaccines. What needs to be learnt now is which specific types of messages are most likely to increase trust in vaccines when delivered in person by health workers. As programs are rolled out in the field, an experimental approach could be adopted to ensure as much is learnt as possible about how vaccine hesitancy can be improved in practice.

We believe there is also scope to learn more about the most effective interventions involving norms. We used one particular phrase designed to suggest that vaccine uptake was common. This had some effect, at least on a subset of the population. However, there are many ways to suggest a community norm exists. It may be the case that other phrases and approaches are more effective at this task. There is scope for further research trying to discover which approaches are most effective at evoking community norms.

Finally, from a more theoretical perspective, there is scope for further work investigating why some of our experimental treatments were quite effective in reducing vaccine hesitancy, in contrast to the treatments in many studies from OECD countries. It would be very useful to learn whether differences stem from different country contexts, different experimental treatments, or differing types of opposition to vaccines – perhaps our experiment was successful simply because vaccine hesitancy in PNG is genuine hesitancy associated with trying a new medical intervention as opposed to being an entrenched position associated with particular world views. There is a need for more learning in this area.

# **7. Reference list**

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