Most of the COVID-19 vaccines require two doses, at least 3 weeks apart. In the first few months of vaccine deployment, vaccine shortages will be inevitable. Current vaccine prioritization guidelines for COVID-19 vaccines all assume two-dose vaccine deployment. However, vaccinating twice as many people with a single dose of vaccine might be a better use of resources. Utilizing an age-stratified mathematical model combined with optimization algorithms, we determined the optimal vaccine allocation with one and two doses of vaccine to minimize five key metrics of disease burden (total infections, symptomatic infections, deaths, peak non-ICU and ICU hospitalizations) under a variety of assumptions (different levels of social distancing, vaccine availability, vaccines mode of action, vaccination rate). Our results suggest that maintaining current social distancing interventions and speedy vaccine deployment are key for successful vaccination campaigns. Further, we show that the optimal allocation of vaccine critically depends on the single-dose efficacy (SDE). If the SDE is high, then under the majority of scenarios considered, single-dose vaccination is the optimal use of vaccine, preventing up to 48% more deaths than a strategy allocating vaccine to the high-risk (older age groups in our model) first. If the SDE is low or medium, then our results suggest that mixed vaccination campaigns with one and two doses of vaccine are best. Our work suggests that it is an absolute imperative to quickly and fully determine the efficacy of single-dose vaccines, as single-dose vaccinations can put an end to this pandemic much more quickly.