A comprehensive understanding of the ethics of the COVID-19 pandemic priorities must be sensitive to the influence of social inequality. We distinguish between ex-ante and ex-post relevance of social inequality for COVID-19 disadvantage. Ex-ante relevance refers to the distribution of risks of exposure. Ex-post relevance refers to the effect of inequality on how patients respond to infection. In the case of COVID-19, both ex-ante and ex-post effects suggest a distribution which is sensitive to the prevalence social inequality. On this basis, we provide a generic fairness argument for the claim that welfare states ought to favour a healthcare priority scheme that gives particular weight to protecting the socially disadvantaged.