A standardized approach for measuring multivariate equity in vaccination coverage, cost-of-illness, and health outcomes: Evidence from the Vaccine Economics Research for Sustainability & Equity (VERSE) project

Following a call from the World Health Organization in 2017 for a methodology to monitor immunization coverage equity in line with the 2030 Agenda for Sustainable Development, this study outlines a standardized approach for measuring multivariate equity in vaccine coverage, economic impact, and health outcomes. The Vaccine Economics Research for Sustainability & Equity (VERSE) composite vaccination equity measurement approach is derived from literature on the measurement of socioeconomic inequality combined with measures of direct unfairness in healthcare access. The final metrics take the form of a concentration index for vaccination coverage where individuals are ranked by multivariate unfairness in access and an absolute equity gap representing the difference in coverage between the top and bottom quintiles of individuals ranked by multivariate unfairness in access. Regression decomposition is applied to the concentration index to determine each factor's relative influence on observed inequity. These methods are applied to India's National Family Health Survey (NFHS) from 2015 to 2016 to assess the equity in being fully-immunized for age vaccination coverage and zero-dose status. The multivariate absolute equity gap is 0.120 (SE: 003) and 0.371 (SE: 0.008) for zero-dose status and fully-immunized for age, respectively. Therefore, the most disadvantaged quintile is 12 percentage points more likely to be zero-dose than the most advantaged quintile and 37.1 percentage points less likely to be fully immunized. The primary correlate of unfair disadvantage for both outcomes is maternal education accounting for 27.4% and 19.1% of observed inequality. The VERSE model provides a standardized approach for measuring multivariate vaccine coverage equity. It also allows policymakers to determine the relative magnitude of factors influencing multivariate equity rather than only the correlates of socioeconomic or bivariate equity. This framework could be adapted to track equitable progress toward Universal Health Coverage (UHC) or outcomes beyond the vaccine space.