US health officials are urging Americans not to be complacent and to use every tool at their disposal to prepare for the Omicron variant of Covid-19, which was recently deemed a “variant of concern” by the World Health Organization.

The overall global risk related to the newly discovered B.1.1.529 strain of the novel coronavirus “is assessed as very high,” the WHO said in a technical brief Monday.

Experts are now racing to determine the answers to these three critical questions:

• Does Omicron’s mutations make it more transmissible?

• Is it more severe/dangerous/deadly than other variants?

• Is it more resistant to vaccines?

It could be weeks before we have the answers.

In the meantime, US travel restrictions on flights from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi went into effect overnight. The Omicron variant was first identified in South Africa and has been detected in multiple countries.

So far, no cases have been confirmed on US soil, but the variant has been detected over the border in Canada, and experts say it will likely pop up in the US soon.

With much about Omicron still unknown, officials say vaccinations and boosters remain the best protection available.

Right now, about 59.1% of the US population is fully vaccinated, and about 19.1% of those fully vaccinated have received a booster dose, according to data from the US Centers for Disease Control and Prevention (CDC).

Omicron reinforces the need for vaccination, Director of the National Institutes of Health Dr. Francis Collins told CNN on Sunday.

“We have to use every kind of tool in our toolbox to keep (Omicron) from getting in a situation that makes this worse,” he said.

“It also means we need to pay attention to those mitigation strategies that people are just really sick of, like wearing masks while indoors with other people who might not be vaccinated and keeping that social distance issue,” he added. “I know, America — you’re really tired of hearing those things. But the virus is not tired of us. And it’s shapeshifting itself.”

Collins also appealed to those who haven’t yet been vaccinated: “If Omicron is one more wake-up call, then let’s wake up. And come on America, you can do this. These vaccines are safe, they’re effective — people have been using them for more than a year, 200 million people plus have gotten injected, these are something you want for yourself, your family, your community,” he said Sunday on Fox News.

Warnings about the renewed threat from the Omicron variant come as Americans have become weary of nearly two years of precautions and are returning from a Thanksgiving break that saw air travel at close to pre-pandemic levels.

Critical 2-week timeline

President Joe Biden is expected to give an update Monday on the US response to Covid-19, the White House said Sunday after Biden met with Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, and other members of the Covid team.

“Dr. Fauci informed the President that while it will take approximately two more weeks to have more definitive information on the transmissibility, severity, and other characteristics of the variant, he continues to believe that existing vaccines are likely to provide a degree of protection against severe cases of Covid,” a readout of their meeting said.

As for immediate recommendations, the White House said the Covid team is recommending boosters for all eligible vaccinated adults.

“This is a clarion call as far as I’m concerned of saying let’s put aside all of these differences that we have, and say, if you’re not vaccinated, get vaccinated. If you’re fully vaccinated, get boosted,” Fauci told NBC News on Sunday.

If tests show antibodies from a person who has been vaccinated can neutralize the Omicron variant of the virus, then “we’re in pretty good shape,” Fauci explained.

“If it looks like even at a high titer of antibody it doesn’t, then what you’ve got to do is you’ve got to change and modify what the vaccine is going to be, which you can do pretty easily,” Fauci said.

Moderna expects to know in a couple of weeks whether the new Omicron variant impacts the efficacy of its vaccine, its chief medical officer said Sunday.

If the company finds it needs to pivot and produce a new vaccine, Moderna is working on several approaches, including one that would be specific to the new variant, Dr. Paul Burton said.

“Our platform, we can move very fast. We think within weeks to maybe two to three months we would be able to have an Omicron-specific vaccine booster available for testing, and then for administration,” he said. “This is going to go at the fastest possible speed, but we have to do careful science now. We don’t want to misstep.”

BioNTech, the German company that partnered with Pfizer to make a Covid-19 vaccine, is also investigating Omicron’s impact on their vaccine, with data expected in the coming weeks.

Johnson & Johnson said it’s also testing the effectiveness of its vaccine against Omicron.

US travel restrictions go into effect

Since the variant was first identified in South Africa, it has also been found in Botswana, Belgium, Canada, Australia, the Netherlands, Denmark, the UK, Portugal, Germany, Israel, Italy, the Czech Republic and Hong Kong.

The US is now restricting travel from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi. Several other countries around the world have introduced similar measures.

While the Biden administration believes the variant will likely show up the US, it instituted travel restrictions to buy time while health experts work to learn more about Omicron’s potential impact.

But on Sunday, the US Travel Association urged the Biden administration to reconsider the restrictions.

“Covid variants are of concern, but closed borders have not prevented their presence in the United States while vaccinations have proven incredibly durable. That is why America’s travel industry is a vocal proponent of everyone getting a vaccine,” the association said in a statement. “With a vaccine and testing requirement in place to enter the US we continue to believe that assessing an individual’s risk and health status is the best way to welcome qualified global travelers into the United States.”

Meantime, passengers arriving at Newark International Airport on a direct flight from Johannesburg Sunday morning described the impact of global travel restrictions.

Kyle Bogert, of Hoboken, New Jersey, told CNN the rest of his family was still stranded in South Africa because their connecting flight through Dubai was canceled as they were on the way to the airport.

“On the news you hear about all these variants popping up in different locations and you hear about airports getting shut down … it’s kind of in the back of your mind until you’re there and you’re stuck there, or your family is stuck there,” he said.

Bogert said passengers on his flight were advised to get tested for Covid-19 “within three to five days,” but noted his exit from his flight was otherwise “normal.”

Passengers were able to fly from Johannesburg to Newark Sunday. (Photo: CNN)