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4 big questions about the new omicron variant

What to watch as scientists race to understand the omicron Covid-19 variant.

A health worker in protective gear puts a nasal swab up the nose of a patient.
A traveler undergoes a Covid-19 test at Sydney International Airport on November 28 in Sydney, Australia.
James D. Morgan/Getty Images
Dylan Scott covers health care for Vox. He has reported on health policy for more than 10 years, writing for Governing magazine, Talking Points Memo and STAT before joining Vox in 2017.

Public health experts have long feared a new, dangerous variant of the novel coronavirus, one that is more deadly, more transmissible, and better able to evade vaccines.

Is the new omicron variant, which has put the world on high alert, it?

Scientists in Botswana and South Africa first detected the variant, which features significant mutations to the coronavirus’s telltale spike protein, a few weeks ago. The sheer number of mutations was reason enough to worry — “this variant is completely insane,” remarked one infectious disease researcher to another — and, over the holiday weekend, the World Health Organization officially named omicron a variant of concern.

That designation means the WHO believes there is good reason to think the omicron variant is more transmissible than the currently dominant delta variant, that it causes more severe disease, or that it can better evade public health measures, including vaccines — or all of the above.

But at this point, there is so much scientists don’t know about omicron. It takes time to collect samples of the variant and study them, to observe transmission patterns, and for enough data to come in to be confident about how the vaccines are handling omicron. It will be at least a couple of weeks before we start to get firm and specific answers to the big outstanding questions.

Only once science has answered those questions will the world know how serious a threat the omicron variant actually is. Is it a minor setback or a major obstacle to getting to a place where we can live with Covid-19? Researchers are racing to find out.

1) How transmissible is the omicron variant?

Covid-19 has evolved to become more contagious over time. The alpha variant, first detected in the United Kingdom ahead of last year’s holiday season, was more easily passed from person to person than the original iteration of the virus. The delta variant, which took over this past spring, was more transmissible than alpha.

Now the question is: Is omicron more transmissible than delta? If so, it will probably reach people without any immunity against Covid-19 — which is still tens of millions of people in the United States and billions across the world — quicker than delta did, and might eventually become the dominant strain of the virus, just as delta displaced previous versions of the coronavirus. As of right now, about 70 percent of all Americans have received at least one dose of a Covid-19 vaccine; worldwide, the share is about 56 percent.

Those odds would also improve if omicron proves better at evading existing immunity (whether from vaccination or prior infection) than delta has been — more on that in a moment. That could cause more reinfections or breakthrough infections.

A version of the virus that is better at evading a person’s immune system could also, in theory, last longer in the body, allowing transmission for a longer period. (The delta variant tends to burn out quickly, in a few days.)

South Africa, one of the world’s leading countries in genetic sequencing and therefore a leading source of data on omicron, has seen a spike in daily Covid-19 cases over the past two weeks — from an average of 246 new cases as of November 14 to 1,851 as of November 28. That has been the basis for much of the concern about omicron being more transmissible.

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Some experts have cautioned that superspreader events could also be contributing to South Arica’s recent spike, and just 29 percent of South Africans have received a dose of the Covid-19 vaccines. One of the things scientists are trying to figure out right now is how much omicron itself is driving the surge there and whether it is likely to do the same elsewhere.

2) Does omicron cause more severe disease?

More transmission would be bad. That means more people getting infected. But the next question is whether omicron is more likely to cause severe disease than delta. That would mean more people getting seriously ill, ending up in the hospital, and dying.

“Because the variant is so new, scientists simply do not have adequate data yet to assess whether the new variant causes more severe disease,” Ashish Jha, dean of the Brown University School of Public Health, wrote over the weekend for the New York Times.

Answering this question will depend on scientists conducting a lot of genetic sequencing on a broad cross-section of virus samples, to be able to compare whether omicron is leading to higher rates of hospitalization than delta has been.

Bill Hanage, a Harvard University epidemiologist, told me he would be watching the hospitalization data in Israel specifically to get an early indication of whether omicron does cause more serious illness. Israel is a well-vaccinated country that has also been aggressive in administering booster shots, he noted: “a proxy for a place that mostly does things right and an early indicator of what can be expected in similar places.”

There has already been some early speculation that omicron may cause milder symptoms, not more severe ones. But the WHO has cautioned that omicron infections being reported so far have tended to be among younger people, who are more likely to have a milder case of Covid-19 no matter the variant.

We just have to wait. “It will most likely take weeks to sort this out,” Jha wrote.

3) How well can omicron evade the Covid-19 vaccines?

The vaccines have been the world’s most effective weapon against Covid-19. So if omicron proves wily in evading the immune response the vaccines are supposed to generate, that would be another big problem.

The concern is a matter of pure biology: The vaccines were designed to target an earlier version of Covid, and omicron may have mutated to the point that it is difficult for the vaccines to identify the virus and send the immune system after it.

“Let’s be clear: It is extremely unlikely that Omicron will render the Covid-19 vaccines completely ineffective,” Jha wrote in the Times. But it is possible that it could make them less effective.

Whether that is the case and to what degree will take time and more data to answer. One possible reason for optimism: For those who have received booster shots, the vaccine may create such an enormous number of antibodies that it still does a good job of fighting off even a highly mutated version of the virus for most people.

“Sometimes quantity can sort of compensate for the lack of match,” Wendy Barclay, a UK researcher focused on new variants, told Stat’s Andrew Joseph.

Another possibility is that the vaccines could be less effective at preventing infections because of omicron’s mutations, but still provide strong protection against severe illness, as has been the case with the delta variant. Stat noted that the vaccines provide several distinct layers of protection for people, so even if omicron breaks through one, the immune system could still be effective at stopping the disease from developing too severely. Trevor Bedford, a scientist at Fred Hutch who studies viruses and immunity, made the same point on Twitter.

But this is all speculative. It will take time to answer this question, along with the related question of whether people who have been previously infected with Covid-19 are more likely to be reinfected with omicron because it evades their immune response.

No matter what, because Pfizer/BioNTech and Moderna used the mRNA platform to create their vaccines, experts are optimistic they could quickly update the vaccines to target omicron and distribute those revised vaccines quickly, should the need arise. Moderna executives said over the weekend that their company could have large quantities of an omicron-specific vaccine available by early 2022.

4) How do the existing Covid-19 treatments hold up against omicron?

One of the reasons for optimism about the trajectory of the pandemic, as recently as a week ago, was the promise of treatments that would significantly reduce the chances of hospitalization or death in people who do get infected with the coronavirus.

Monoclonal antibodies have been available for a while. Both Merck and Pfizer are seeking approval from the Food and Drug Administration for antiviral medications in the form of pills that could prevent severe illness as well. Those developments promised a new normal where, for most people, Covid-19 really could be more akin to the flu: undesirable but manageable.

But, much like the vaccines, omicron has created new uncertainty about how well those treatments will work if the variant becomes dominant. Some experts sound optimistic that the antivirals will be fine because they target parts of the virus that have not mutated, but warn that the effectiveness of monoclonal antibodies could be compromised. Others say it is simply too early to be sure either way.

For now, on all of these questions, that’s a common theme, and there is only one certainty: Time will tell.