Harry Halpin (a researcher and CEO of privacy startup Nym Technologies) wrote a critical article about the standards used by prominent so-called immunity passports. Besides a technical critique of the standards, he also makes some important remarks about the risks related to the obduracy of the technologies:

The question should not be whether or not immunity passports can be technically secure and private, but whether or not they should be built at all. Due to the state of emergency caused by COVID-19, fundamental rights – such as the freedom of movement – could be taken away based on data connected to persistent digital identity. Yet temporary measures meant for a purpose as seemingly harmless as reviving tourism could become normalized as the blockchain-based identity databases are by design permanent and are difficult to disassemble once the crisis has past. Blockchain technology could just as easily allow automated discrimination based on personal data as it could enable travel during COVID-19, and form the technical basis for a ‘social credit’ system that crosses borders.

The full, non peer-reviewed article can be found at arXiv.