Supporters say they could make reopenings faster and easier. Proof of vaccination or a negative test could be a way for businesses and schools to reassure customers, students and parents that steps are being taken to limit transmission of the virus.
International travel bans by countries could also be eased if people are able to show proof they’re vaccinated. Some countries have long had requirements to prove vaccination against yellow fever.
Still, a challenge is creating certification systems that work across vaccine providers and businesses. More than a dozen initiatives are underway to develop a credential that could be stored on a smartphone or printed on paper, using a QR code.