Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study

TLDR

Evidence shows vaccine delays or refusals stem from mistrust of vaccine safety, importance, or effectiveness, and access issues, yet no robust global monitoring system for vaccine confidence exists. The study aimed to map global vaccine confidence across 149 countries from 2015 to 2019. Using 290 surveys of 284,381 individuals, the authors applied a Bayesian multinomial logit Gaussian process model and univariate Bayesian logistic regressions, with Gibbs sampling for inference, to estimate public perceptions and their associations with uptake. Confidence in vaccine importance, safety, and effectiveness declined in several countries, increased in some EU states, and was most strongly associated with uptake, while religious minority status linked to lower uptake, underscoring the need for regular monitoring. Funding was provided by the European Commission, Wellcome, and the Engineering and Physical Sciences Research Council.

Abstract

BackgroundThere is growing evidence of vaccine delays or refusals due to a lack of trust in the importance, safety, or effectiveness of vaccines, alongside persisting access issues. Although immunisation coverage is reported administratively across the world, no similarly robust monitoring system exists for vaccine confidence. In this study, vaccine confidence was mapped across 149 countries between 2015 and 2019.MethodsIn this large-scale retrospective data-driven analysis, we examined global trends in vaccine confidence using data from 290 surveys done between September, 2015, and December, 2019, across 149 countries, and including 284 381 individuals. We used a Bayesian multinomial logit Gaussian process model to produce estimates of public perceptions towards the safety, importance, and effectiveness of vaccines. Associations between vaccine uptake and a large range of putative drivers of uptake, including vaccine confidence, socioeconomic status, and sources of trust, were determined using univariate Bayesian logistic regressions. Gibbs sampling was used for Bayesian model inference, with 95% Bayesian highest posterior density intervals used to capture uncertainty.FindingsBetween November, 2015, and December, 2019, we estimate that confidence in the importance, safety, and effectiveness of vaccines fell in Afghanistan, Indonesia, Pakistan, the Philippines, and South Korea. We found significant increases in respondents strongly disagreeing that vaccines are safe between 2015 and 2019 in six countries: Afghanistan, Azerbaijan, Indonesia, Nigeria, Pakistan, and Serbia. We find signs that confidence has improved between 2018 and 2019 in some EU member states, including Finland, France, Ireland, and Italy, with recent losses detected in Poland. Confidence in the importance of vaccines (rather than in their safety or effectiveness) had the strongest univariate association with vaccine uptake compared with other determinants considered. When a link was found between individuals' religious beliefs and uptake, findings indicated that minority religious groups tended to have lower probabilities of uptake.InterpretationTo our knowledge, this is the largest study of global vaccine confidence to date, allowing for cross-country comparisons and changes over time. Our findings highlight the importance of regular monitoring to detect emerging trends to prompt interventions to build and sustain vaccine confidence.FundingEuropean Commission, Wellcome, and Engineering and Physical Sciences Research Council.