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2. Voo, T. C. et al. Immunity certification for COVID-19: ethical considerations. Bull. World Health Org. 99, 155–161 (2021).
3. Brown, R. C. H., Kelly, D., Wilkinson, D. & Savulescu, J. The scientific and ethical feasibility of immunity passports. Lancet Infect. Dis. 21, e58–e63 (2021).
4. European Commission, Directorate-General for Justice and Consumers. Proposal for a REGULATION OF THE EUROPEAN PARLIAMENT AND OF THECOUNCIL on a framework for the issuance, verification and acceptance of interoperable certificates on vaccination, testing and recovery to facilitate free movement during theCOVID-19 pandemic (Digital Green Certificate, Document 52021PC0130) https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:52021PC0130 (2021).
5. European Commission, Directorate-General for Justice and Consumers. Regulation (EU)2021/954 of the European Parliament and of the Council of 14 June 2021 on a framework for the issuance, verification and acceptance of interoperable COVID-19 vaccination, test and recovery certificates (EU Digital COVID Certificate) with regard to third-country nationals legally staying or residing in the territories of Member States during the COVID-19 pandemic (Text with EEA relevance), Document 32021R0954 https://eur-lex.europa.eu/legal-content/en/TXT/?uri=CELEX:32021R0954 (2021).