While overall mortality from measles has decreased, it is still associated with significant global infant deaths. Studies indicate that a second dose of measles-containing vaccine (MCV) is necessary to produce sufficient immunity to measles, yet several developing countries are deficient of a two-dose schedule. This study examined the efficacy of three economic indices—the Human Development Index (HDI), the Inequality-adjusted Human Development Index (IHDI), and the Multidimensional Poverty Index (MPI)—in predicting first-to-second MCV dosage disparities. Country-level data for MCV coverage were downloaded from the World Health Organization (WHO). Briggsian logarithmic regression models of MCV dosage disparities were calculated to compare the predictive power of the HDI, IHDI, and MPI. The MPI explained the most variance in dosage disparities, F (1, 54) = 41.835, p < 0.001, R2 = 0.437, b = 0.938, followed by the IDHI (R2 = 0.361, b = −0.935) and HDI (R2 = 0.354, b = −1.023). We suggest the MPI explained the greatest variance because it uses multiple indicators to determine poverty across three dimensions of human development. The MPI predicted larger disparities in more developing countries. Future efforts should be directed toward discovering and reducing barriers to second dose MCV administration in these countries.