  Motivated by COVID-19 vaccine allocation, where vulnerable subpopulations are
simultaneously more impacted in terms of health and more disadvantaged in terms
of access to the vaccine, we formalize and study the problem of resource
allocation when there are inherent access differences that correlate with
advantage and disadvantage. We identify reducing resource disparity as a key
goal in this context and show its role as a proxy to more nuanced downstream
impacts. We develop a concrete access model that helps quantify how a given
allocation translates to resource flow for the advantaged vs. the
disadvantaged, based on the access gap between them. We then provide a
methodology for access-aware allocation. Intuitively, the resulting allocation
leverages more vaccines in locations with higher vulnerable populations to
mitigate the access gap and reduce overall disparity. Surprisingly, knowledge
of the access gap is often not needed to perform access-aware allocation. To
support this formalism, we provide empirical evidence for our access model and
show that access-aware allocation can significantly reduce resource disparity
and thus improve downstream outcomes. We demonstrate this at various scales,
including at county, state, national, and global levels.
