Fauci says that he believes that the government will not mandate vaccine passports. He probably right. They won't mandate them because then a Constitutional contest will bring the whole house of cards down to the ground.
What they are going to do instead is what's been working so far. The feds will provide 'guidance'. This makes it so corporations and private entities have something to use to implement the passports instead. They'll just be able to say that they are following fed.gov guidance--not rules, not regs, nothing that is actionable in court.
Attorneys General all over the US are 'reminding' people that even if there are no government mandates, then private companies can put into place any rules they want for use of their services and to access their properties. Private companies are proving themselves to be part of the military-industrial-entertainment complex that Fox Mulder warned us about on the X-Files. Look at Coke, MLB, Delta--all Biden had to do is say he supported a boycott of the State of Georgia and poof. Look at Meijer, Walmart, Menards, Target, Home Depot, Kohls, etc. etc. with their quick implementation of the use of masks in their stores and keeping those rules in place, regardless of governmental mandates. Look at FaceBook, Google, Twitter and their selective censorship. Look at CBS creating outright lies.
The government provides the umbrella, the corporations are the tool of the government. We the People are screwed.