The United States just recently started allowing international visitors into the countries, but a new COVID-19 variant already has travel restrictions back in place.

Omnicron, believed to have originated in South Africa, has prompted President Joe Biden to place travel restrictions for eight countries in southern Africa.

Dr. John Zaso, a pediatrician at NYU Langone Health, says it is a highly evolved mutation that could be much more contagious.

It's not clear how the current vaccines work against the new strain, but Zaso says their effectiveness could go down.

"If you think of the spike protest as a key--what happens is you have many teeth on a key," Zaso says. "Sometimes one tooth can be a little off or flat and it can still work. When you a 30-mutation spike protein, it's a whole new key."

Robert and Melissa Silverstein were planning a trip to Aruba, but changed their minds because of the new variant.

"It's scary," Robert Silverstein says. "But it's just something we need to find out more about."

News of the new variant also sent stocks tumbling after the holiday as scientists look to learn more about it.

Zaso says it's not yet known if there is any increase in how sick the Omnicron makes someone, but he says it's "probably" very contagious compared to other strains.

Travel restrictions begin on Monday. They do not apply to United States citizens or permanent residents, but traveling to that part of the world is not advised.