I have two concerns about Pugh et al ’s case that vaccine requirements without a natural immunity exception are unjustified.1 First, the scientific question they suggest must be answered to justify the policy is in my view the wrong one, or at least not the only relevant one. Second, the authors set up a standard for public health regulation that will be often unattainable, risking paralysis of public health authorities. Pugh et al suggest two legitimate bases for vaccine mandates: ‘the (...) prevention of severe outcomes from COVID-19 and the reduction of viral transmission.’ Governments and employers have a legitimate interest in protecting the health of their citizens and workers, respectively. To maximally accomplish these goals, the relevant scientific question for whether people with prior infection should be subject to a vaccine mandate is: in persons who have been previously infected, does vaccination enhances protection against severe disease and/or infection and transmission? The relevant comparison, if one is trying to maximise protection in the population, is not vaccination vs prior infection, but vs prior infection alone. I am unaware of a systematic review of this question, but the answer in two recent studies appears to be that the combination is more protective.2,3 The comparison the authors propose, in contrast, seems to be one based on an unstated conception of fairness and adequacy: if vaccination alone provides some level of protection, and prior infection can’t be shown to provide an inferior level, then prior infection should be an acceptable alternative to vaccination to satisfy mandates. No argument is given to support the greater relevance of the comparison the authors emphasise. A second and independent concern is that the authors’ proposal …. (shrink)