There is much debate about the use of immunity passports in the response to the COVID-19 pandemic. Some have argued that immunity passports are unethical and impractical, pointing to uncertainties relating to COVID-19 immunity, issues with testing, perverse incentives, doubtful economic benefits, privacy concerns, and the risk of discriminatory effects. We first review the scientific feasibility of immunity passports. Considerable hurdles remain, but increasing understanding of the neutralising antibody response to COVID-19 might make identifying members of the community at low risk of contracting and transmitting COVID-19 possible. We respond to the ethical arguments against immunity passports and give the positive ethical arguments. First, a strong presumption should be in favour of preserving people's free movement if at all feasible. Second, failing to recognise the reduced infection threat immune individuals pose risks punishing people for low-risk behaviour. Finally, further individual and social benefits are likely to accrue from allowing people to engage in free movement. Challenges relating to the implementation of immunity passports ought to be met with targeted solutions so as to maximise their benefit.