To pre-empt ad hoc vaccine mandates by private actors, governments should prioritize thoughtful and context-dependent regulation of vaccination certificates. Ten months after we detailed myriad problems with immunity passports for COVID-19 (N. Kofler and F. Baylis Nature 581, 379–381; 2020), our ethical concerns have only grown. These are: inequality with respect to fair vaccine access, compromised privacy, heightened social stratification, increasing discrimination against minority ethnic and other marginalized groups, and the introduction of new forms of discrimination.

In specific circumstances to protect public health, proof of vaccination could be important, say, for those who live or work in long-term care facilities or for doctors and nurses — similar to influenza vaccine mandates for health-care workers in some US states. However, broad application of mandated vaccine certification for discretionary travel — or to access restaurants, sporting events, gyms, concerts and other leisure facilities — sharpens each of our concerns about increasing inequity.

Policy should be informed by a public-health ethic focused on the common good. It should aim to bolster community health by protecting those most vulnerable to COVID-19, not to entrench existing inequities that exacerbate those vulnerabilities.