FILE - In this undated photo, provided by NY Governor's Press Office on Saturday March 27, 2021, is the new "Excelsior Pass" app, a digital pass that people can download to show proof of vaccination or a negative COVID-19 test. Vaccine passports being developed to verify COVID-19 immunization status and allow inoculated people to more freely travel, shop and dine have become the latest flash point in America’s perpetual political wars, with Republicans portraying them as a heavy-handed intrusion into personal freedom and private health choices. (NY Governor's Press Office via AP, File)

FILE - In this Tuesday, Jan. 5, 2021, file photo, a woman receives a dose of the COVID-19 vaccine from a pharmacist at Nassau County's first vaccination distribution site, set up by Northwell Health and Nassau County, at Nassau County Community College, in Garden City, N.Y. Vaccine passports being developed to verify COVID-19 immunization status and allow inoculated people to more freely travel, shop and dine have become the latest flash point in America’s perpetual political wars. (AP Photo/Kathy Willens, File)

FILE - In this Tuesday, Feb. 23, 2021, file photo, a man presents his "green passport," proof that he is vaccinated against the coronavirus, on opening night at the Khan Theater for a performance where all guests were required to show proof of vaccination or full recovery from the virus, in Jerusalem. Vaccine passports are being developed in the U.S. to verify COVID-19 immunization status and allow inoculated people to more freely travel, shop and dine. (AP Photo/Maya Alleruzzo, File)

FILE - In this Wednesday, March 17, 2021, file photo, travelers walk through the Salt Lake City International Airport, in Salt Lake City. Vaccine passports being developed to verify COVID-19 immunization status and allow inoculated people to more freely travel, shop and dine have become the latest flash point in America’s perpetual political wars, with Republicans portraying them as a heavy-handed intrusion into personal freedom and private health choices. (AP Photo/Rick Bowmer, File)