Just like a national passport, a vaccine passport could allow the bearer entrance to a venue, like a crowded concert, or a foreign country that demands proof of vaccination in addition to a visa and valid national passport.

Vaccination cards from the US Centers for Disease Control and Prevention aren't quite the same as a vaccine passport.

What exactly is a vaccine passport?

A vaccine passport is just proof that a person has been immunized against Covid-19.

Greg Abbott this week signed an order prohibiting the state's agencies from requiring a vaccine for any service.

"Government should not require any Texan to show proof of vaccination and reveal private health information just to go about their daily lives," Abbott said in a video posted on Twitter.

Who issues vaccine passports?

There's a lot of talk and debate about the passports, but hardly anyone is issuing them yet -- though they are available in New York to vaccinated residents.

While the Biden administration has been trying to find a way toward a standard for vaccine certification, the federal government will not issue a vaccine passport, White House Press Secretary Jen Psaki said Tuesday.

Pros and cons of a vaccine passport

The pros and cons of requiring a vaccine passport were encapsulated by business owners and managers in Florida, where the passports have been banned.

Rocco Mangel, who owns Rocco's Tacos and Tequila Bar in Delray Beach, said he has been vaccinated and would like others to be as well, but requiring his customers to have proof of vaccination to come into the restaurant "infringes on their rights," he told CNN.