Researchers are still learning about Covid's new omicron variant, but one expert has a stark prediction.

"All the scientists I've talked to... are like, 'This is not going to be good,'" Moderna CEO Stéphane Bancel told the Financial Times on Tuesday.

On Sunday, at least two omicron cases were detected in Canada, marking its arrival in North America — roughly two weeks after the variant was first detected in South Africa, on November 9. White House chief medical advisor Dr. Anthony Fauci said he "would not be surprised" if omicron is already in the United States, in an interview with NBC's "Weekend TODAY" on Saturday.

The next few weeks will be telling, as scientists analyze how effective the Covid vaccines are against omicron and countries crack down on testing and tracing to identify where the variant is. The World Health Organization said Monday that omicron poses a "very high" global risk.

In the meantime, multiple states have warned people to stay vigilant. New York City is back to "strongly recommending" masks in all indoor public settings, regardless of vaccination status, Dr. David Chokshi, commissioner of the New York City Department of Health and Mental Hygiene, told reporters Monday.

You may have questions about what this means for you. Here's what you need to know:

Is omicron more dangerous than other variants?

Omicron contains troubling characteristics that might make it more transmissible — particularly among people who have already gotten and recovered from Covid, according to the WHO.

Most notably, the variant contains "a disturbingly large number of mutations in the spike protein," Fauci told ABC's "This Week" on Sunday. The spike protein is the part of the virus that latches onto and penetrates cells in your body, leading to a Covid infection.

Omicron has more than 30 spike protein mutations, compared with the original virus — significantly more than the delta variant. The function of those mutations isn't fully known yet, but some of them could make it easier for the virus to infiltrate human cells.

The WHO noted on Friday that "infections have increased steeply" in South Africa, in tandem with the discovery of omicron. Only 24% of the population in South Africa is vaccinated, compared to 59% of the U.S. population. Still, other countries can expect a similar pattern to unfold as the variant spreads, Fauci said.

Here's some potentially good news: So far, omicron hasn't caused any known deaths, and its symptoms appear to be "extremely mild," Dr. Angelique Coetzee, chair of the South African Medical Association that discovered the variant, told the BBC on Sunday.

If true, that could mean omicron's mutations make it more easily transmissible, but less severe. (According to the WHO, there's no consensus yet that omicron symptoms differ from other variants.)

Do the vaccines already protect against omicron?

It's too soon to tell — which isn't reason for panic. It just means scientists are working on finding out.

Given omicron's plentiful mutations, it could theoretically evade vaccine-induced protection. Bancel said he anticipates a drop in vaccine effectiveness. Researchers will likely have answers within the next two weeks by testing antibodies from people who are vaccinated, and seeing if they are capable of neutralizing the virus.

Even if omicron can evade those antibodies, the vaccines are still likely to protect against severe illness, BioNTech CEO and co-founder Dr. Ugur Sahin told the Wall Street Journal on Tuesday. That's because omicron will "hardly be able to completely evade T-cells," which are the body's second line of defense against the virus, Sahin said.

Still, President Joe Biden instructed the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention on Monday to use the "fastest process available without cutting any corners," to make omicron-specific vaccines available, if necessary.

It's unclear who would be eligible for those vaccines, if they eventually get approved.

Moderna says it's already working on one, which could be ready to ship by early 2022, if necessary. On Monday, Pfizer CEO Albert Bourla told CNBC's "Squawk Box" that his company is waiting for more data before acting — but could have its version ready in 100 days.

Non-vaccine treatments could also be a mixed bag. Pfizer's Covid antiviral pill, Paxlovid — which has yet to be approved by the FDA — might work against variants like omicron, because it's designed to address spike mutations, Bourla said.

But fellow drugmaker Regeneron said Tuesday that its monoclonal antibody cocktail, along with any other similar drugs, could be less effective against omicron than other variants. The company said it's exploring other alternatives.

Should you wait on getting a booster until there's an omicron-specific shot?

No. Get your booster as soon as you're eligible, regardless of any omicron developments.

Even partial protection is better than no protection, and the longer you wait, the more you risk getting infected by another Covid variant — including delta, which remains dangerous.

Plus, if the current Covid vaccines prove effective against the new variant, omicron-specific shots may never be deemed necessary. Waiting for that answer is a gamble akin to playing "mind games," Fauci told "Meet the Press."

In a statement on Monday, CDC director Dr. Rochelle Walensky specifically cited omicron as a reason why eligible people should get their boosters. Since the booster shot lifts your body's level of antibodies high enough to protect against every other known variant, it should give you "at least some degree, and maybe a lot of protection" against omicron, Fauci said.

What should you do differently to protect yourself against omicron?

Getting vaccinated and boosted, plus wearing a mask in public indoor settings, remain the best ways to protect yourself and the people around you.

"Do not pull back on your guard," Fauci told NBC's "Weekend TODAY."

On Monday, the Biden administration restricted most air travel from South Africa and seven other countries: Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia and Zimbabwe.

Travel bans cannot completely prevent the virus from entering the country, but they "delay it enough to get us better prepared," Fauci said. Lockdowns aren't currently being discussed, Biden said Monday.

Even if omicron gets bad, it probably won't undo the world's Covid-fighting progress.

Tests can easily detect omicron, promising therapeutics like the antiviral pills are on the horizon and scientists know much more about the disease than they did in March 2020, Dr. Ashish Jha, dean of the Brown University School of Public Health, tweeted on Sunday.

Update: This story has been updated to include BioNTech CEO Dr. Ugur Sahin's comments on Covid vaccine effectiveness against the omicron variant.

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