A passport proves your identity. A digital one could confirm that you've gotten a COVID-19 vaccine and, in some cases, that you're negative for the virus.
The digital vaccine passport idea is one the United States and other countries are considering, but cybersecurity experts and doctors say there are some big red flags.
"Just by having a vaccination, depending on the vaccine you have, doesn’t mean you have immunity to COVID," UCSF infectious disease expert Dr. Peter Chin-Hong said. "There’s regular COVID, which we know the data from, and also there are variants circling around."
Last month, the World Health Organization released a statement with a similar message, saying, "At the present time, do not introduce requirements of proof of vaccination or immunity for international travel as a condition of entry as there are still critical unknowns regarding the efficacy of vaccination in reducing transmission and limited availability of vaccines."
Supporters of the passport program say it would help the tourism economy and struggling businesses like the airline industry, but cybersecurity experts worry about hacking and other issues with people's medical and personal information.
"There is so many moving parts in this project that we have to be careful about it because each one of them is a nightmare for privacy, security and safety," San Jose State University professor and cybersecurity expert Ahmed Banafa said.
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Last weekend, Israel launched a digital vaccination passport program called "Green Pass."
It's a new app linked to people's medical files so they can prove they've been vaccinated or that they've recovered from COVID-19 and have immunity.
Anyone with a "Green Pass" can travel within the country and has access to places like gyms, theaters and hotels.
"If you get an immunity passport, I would still be a little bit nervous about folks taking their masks off on a plane, for example," Chin-Hong said.
President Joe Biden has asked several government agencies to start looking into digital international vaccination certificates.
Tech giants in the U.S. are now also racing to a build a system for digital passports.