The COVID-19 pandemic, particularly the period when safe and protective vaccines became available, presented an excellent opportunity to investigate public preferences regarding how to ration a scarce, life-saving resource. It is important to understand which distributive strategies are preferred but, as this is an inherently normative matter, also to which extent different socio-demographic groups hold different opinions. This study assesses the impact of socio-demographic characteristics on preferences for vaccine prioritization during the early stages of the COVID-19 pandemic at the moment when vaccines were not available yet. A representative sample of 2060 Belgians were asked to rank eight prioritization strategies. Based on the rankings, we clustered the eight strategies into five overarching groups. Then, we estimated the potential impact of respondents' socio-demographic characteristics on their preferences towards these five strategies. The ranking exercise shows that the vulnerability strategy (i.e. chronically ill and elderly) is preferred most often (N = 1815) and the market strategy (i.e. individuals who come first or pay the most) by the fewest respondents (N = 116). Preferences for vaccine distribution vary among population subgroups. Women, older or retired individuals, residents of Flanders, those with a positive attitude towards vaccination efforts and/or high vaccination willingness, and those who prefer the government or scientists to decide upon prioritization were more likely to prefer a designated priority strategy (i.e. vulnerability strategy, workers strategy or spreaders). Furthermore, younger respondents, residents of Wallonia, and those previously infected by COVID-19 tended to favour a risk-independent prioritization strategy (i.e. lottery or market strategy) more than others. This study validates the appropriateness of the implemented rationing approaches, by supporting a phased approach in which first vulnerables were vaccinated. However, it also demonstrates that different subgroups had substantially different preferences and the population was in disagreement about what constitutes a fair rationing policy for a scarce, potentially lifesaving resource.