Creating the vaccination improvement potential index.

Background: Numerous social and behavioral factors have been implicated in vaccination coverage. There is no single measure that describes a country's ability to improve or maintain its immunization coverage. Methods: We estimated the "Vaccination Improvement Potential" (VIP) by taking the geometric mean of 13 different indicators on health financing, vaccine confidence, and socio-demographics for more than 200 countries across 30 years. Potential VIP Index values range from 0 to 1, with a higher score indicating greater potential to improve or maintain high vaccination rates. Findings: In 1990, the mean VIP score was 0.49 (range = 0.13 to 0.86). In 2019, the mean score was 0.59 (range = 0.25 to 0.84). Consistent high performers included countries in Western Europe and high-income North America and East Asia. Important differences in subcomponents of the index drove major trends including vaccine hesitancy in Western Europe and Asia as well as lower levels of per capita health spending and development assistance in sub-Saharan Africa. Interpretation: The VIP Index is a first-of-its-kind tool for understanding the capacity that exists in a country to realize improved immunization rates. It is a new resource that can guide researchers, policymakers, and health officials to more effectively deploy resources to realize improvements in vaccination coverage, assess the impact of those improvements, and identify countries that might require additional support to improve vaccine coverage. Funding: Merck Sharp & Dohme Corp.