COVID-19 live updates: City sees fourfold increase in pediatric hospitalizations

Maryland Gov. Larry Hogan said he tested positive for COVID-19 Monday morning.

Hogan, a cancer survivor, said he's vaccinated and booster and is "feeling fine."

-ABC News' Alisa Wiersema

The Israeli government on Monday passed a resolution adding the United States and Canada to its "red list," banning its citizens from traveling to those countries.

The ban, which would also stop visitors from those countries from entering Israel, is scheduled to go into effect Tuesday night at midnight local time, the prime minister's media advisor said in a statement following Monday's vote.

The Knesset Constitution, Justice and Law Committee has to approve the measure, which was recommended by the Health Ministry State Classification Committee.

Israeli citizens returning from "red list" countries must quarantine. Israelis are now barred from travelling to Belgium, Germany, Hungary, Italy, Morocco, Portugal, Switzerland and Turkey.

The omicron surge is so dangerous due to a combination of higher transmissibility and the variant's ability to make vaccinated people mildly sick from the disease, Dr. Ashish Jha, dean of the Brown University School of Public Health, said on "Good Morning America" Monday.

While there are still a lot of unknowns about omicron's severity, Jha said cases with this latest variant's surge are "doubling in numbers about every two to three days."

"That’s unlike anything we've seen," he said.

Jha said, "I do think lots of people are going to get [omicron]."

"It's an incredibly contagious variant. I think people should understand that the goal cannot be to avoid infection at all cost -- that's an unrealistic goal," he said. "The goal should be: prevent deaths and severe illness, which vaccines will do, [and] keep our hospitals from getting crushed, which again, vaccinations and testing can help with. This is very contagious. Lots of Americans will end up getting it. Let's just make sure that they don't get very sick from it. "

For people traveling over the holidays, Jha said airplanes are pretty safe, but he recommended wearing a high-quality mask because airports don't always have great ventilation.

Looking forward, Jha said, "I think we're going to be in much better shape next year."

The vaccines have already been in the U.S. for one year, Jha said, and he predicted the omicron surge will build more immunity.

"I am not saying COVID will be gone next winter. It will be around, but we should be able to get better and better at managing it," Jha said. "This winter is so much better than last year and I expect next winter will be so much better than this year."

Moderna on Monday said its current vaccine booster increased neutralizing antibodies against omicron within a month of getting the shot.

“The dramatic increase in COVID-19 cases from the Omicron variant is concerning to all," Stéphane Bancel, Chief Executive Officer of Moderna, told ABC News. "However, these data showing that the currently authorized Moderna COVID-19 booster can boost neutralizing antibody levels 37-fold higher than pre-boost levels are reassuring.”

Moderna's currently approved booster is a 50-microgram dose. A 100-microgram dose would increase neutralizing antibodies by 83 times, the company said on Monday.

The company's also working to "rapidly advance" its omicron-specific booster into clinical testing, Bancel said.

“We will also continue to generate and share data across our booster strategies with public health authorities to help them make evidence-based decisions on the best vaccination strategies against SARS-CoV-2,” he said.