The International Air Transport Association (IATA) is launching a system of digital ‘passports’ as proof that passengers have been vaccinated against COVID-19 (see go.nature.com/2ke7rhv). The data are stored on the traveller’s electronic device, which seems barely more advanced than the decades-old international paper certificate of vaccination or prophylaxis. Furthermore, uploading the data to an IATA or technology-company database risks compromising security and confidentiality.
Critics have questioned the ethics of using proof of vaccination for personal advantage (N. Kofler and F. Baylis Nature 581, 379-381; 2020). In this and other respects, blockchain technology would offer a superior data-storage system for vaccination records. A decentralized blockchain ledger would be anonymous, immutable and transparent. Entries can be publicly audited. Anonymity is protected, with access only with a private key or authorized biometrics. Storage is a non-issue, because data are not controlled by a centralized authority.
That said, issuing ‘immunity passports’ might be premature — first we need more information on the immunity conferred by different COVID-19 vaccines and the impact of SARS-CoV-2 variants.