Figueiredo and Larson (2021) found a positive association between belief the government was handling the crisis well and willingness to be vaccinated in a sample of 32 countries with various income levels. Lazarus and colleagues reported the same, but only in bivariate odds ratios. Future analysis is needed to investigate this relationship, preferably using an individual level measure of trust in government rather than the national-level measure used in this analysis.

With respect to our results on changes over time, which showed that changes were minimal in all countries except Iraq, Malawi, and Uzbekistan, where we report relatively large increases. It is difficult to identify the factors that led to increased hesitancy in these cases. The larger body on changes over time in vaccine hesitancy during the same timeframe as the HFPS data were collected is mostly from highincome countries and shows mixed results: increased rates of vaccine hesitancy reported in Australia, Canada and the United States between April and December 2020 (To et al. 2021, Lavoie et al. 2022, Szilagyi et al. 2020), rates remained stable in Italy between June 2020 and January 2021 (Basio et al. 2022) and decreased in Greece between November 2020 and May 2021 (Sypsa et al. 2022).

The main reasons reported in the HFPS regarding COVID-19 vaccine hesitancy, which mainly revolve around safety and to a lesser degree efficacy, are consistent with the few studies that report reasons for COVID-19 vaccine hesitancy in low- and middle-income countries and with the main reasons for vaccine hesitancy historically. Solis Arce and colleagues (2021) also reported concerns about side effects to be the most frequently expressed reason in their sample of low- and middle-income countries. Facebook survey results for the same month were available for 21 countries, although reasons for not getting vaccinated were collected separately for respondents who would “definitely not” and “probably not” take the COVID19 vaccine and multiple reasons were collected. Nevertheless, they show that concerns about safety (worded as “concern about side effects” or “wait and see if it’s safe”) were the primary concern, followed in most countries by either concerns about efficacy or lack of trust in the government (Figure 11).

Concerns have been raised about supply constraints – both lack of vaccine supply and lack of infrastructure to deliver the vaccines -- being the greatest barrier to COVID-19 vaccination scale-up in developing countries. This study did not find this to be a major concern for respondents (6% average across all surveys with the single answer option). As we noted above, however, the relative incidence of supply-side concerns in the HFPS data may be influenced by the framing of the question, as respondents may have interpreted the question whether they would get vaccinated “when the vaccine becomes available,” as indicating a time when current access constraints get resolved. Furthermore, there was a set of small countries in Latin America where over 10% of respondents cited supply constraints as their main concern, specifically “health center too far or hard to reach” or “I don't have time to go to get vaccinated.” This finding reinforces the importance citizens place on having easy and quick access, especially in Caribbean countries that are highly dependent on tourism.

Counterindication – that is, believing one should not be vaccinated due to pre-existing health conditions – has been identified has a significant barrier to vaccination in Eastern Europe and Central Asia (World Bank, UNIFEF and JICA 2021). In Georgia, Tajikistan, Uzbekistan, and Kazakhstan, the most common reason for hesitancy was not being eligible (World Bank, UNIFEF and JICA 2021). Indeed, in many countries in that region, medical regulations recommend against vaccination for anyone with a preexisting medical condition. In Uzbekistan it was found that medical personnel interpreted the regulation even more strictly than it was written, regularly refusing to vaccinate persons with a pre-existing condition. For these countries, two policy responses may help to address this challenge: revising standard regulations (which 21