Resource planning during pandemics presents many challenges and equitable decisions about resource allocation must be made. There is no standard definition of equity. Robust mathematical formulations can require a lot of data. In a novel pandemic there is limited historical information available to inform decisions. Decision makers can look to define equity through population proportions (pro-rata). This notion of equity is readily implementable. We present a practical framework for an equitable allocation of scarce resources using population proportions, disease demographics, and resource utilization. We assess our framework using a stochastic simulation model, calibrated to COVID-19 case data, in a case study for convalescent plasma distribution in the context of the clinical trial CONCOR-1. We show that pro-rata resource allocation can be inequitable and that decision makers can consider readily available information, such as resource utilization and case data, to inform equity and proactively manage scarce resources during a pandemic.