A COVID vaccine requirement should "seriously" be considered for domestic air travel in the U.S. as a response to the Omicron variant of the virus, NIAID director Anthony Fauci told MSNBC's "Morning Joe" on Monday.

Why it matters: The U.S. is now experiencing another wave of coronavirus cases driven by the Omicron variant.

• Early data from South Africa, where the variant was first discovered, suggests that it spreads easier but may cause milder disease than previous variants.

What he's saying: “When you make vaccination a requirement, that’s another incentive to get more people vaccinated,” Fauci said. “If you want to do that with domestic flights, I think that’s something that seriously should be considered.”

• "The group we're really concerned about is the unvaccinated people because even if this virus is inherently less severe, just the volume of the number of cases that we're going to have could actually put a stress on the hospital system," he said earlier in the interview.

The latest: Fauci on Monday evening clarified that he does not expect such a mandate to be implemented "in the reasonably foreseeable future.”

• "It's on the table, and we consider it, but that doesn't mean it's going to happen," he told CNN.

The big picture: Fauci also said the CDC is considering shortening the isolation and quarantine time for essential workers who have been exposed to or contracted the virus, after it shortened the quarantine time for health care workers last week.

Go deeper: The ongoing U.S. failure on rapid COVID tests

Editor's note: This post was updated with Fauci's later comment that he does not expect that a vaccine mandate for domestic flights to be implemented soon.