Omicron and other coronavirus variants: What you need to know

Reviewed by Emily Henderson, B.Sc.Nov 30 2021

Americans, already weary of a pandemic nearly two years long, were dealt a new blow during the long Thanksgiving weekend: the announcement that a new coronavirus variant had emerged.

The omicron variant, officially known as B.1.1.529, surfaced in November in several southern African nations. It set off alarm bells worldwide when public health officials in South Africa saw it beginning to outcompete the previous reigning variant, delta. This suggested that omicron could eventually spread widely. Indeed, omicron has since been reported on multiple continents, likely due to international travel by people unknowingly infected.

After the emergence of omicron was announced, several nations imposed travel bans hoping to contain the virus. Whether those bans will effectively slow the spread remains unknown. “Travel bans don't help once the horse is already out of the barn, as we've seen before and are seeing now,” said Tara Smith, a Kent State University epidemiologist.

Scientists caution that it's still too early to say whether omicron will prove as dangerous as delta. Other variants that initially seemed worrisome have flamed out.

For now, here's what we know, and don't know, about the omicron variant.

What is a variant?

A variant of a virus is one that has mutated in a way that bolsters its spread or severity compared with the original strain that emerged in Wuhan, China. “RNA viruses like the coronavirus can mutate when they replicate, especially when circulating at high rates,” said Dr. Monica Gandhi, professor of medicine at the University of California-San Francisco.

Coronaviruses do not mutate as readily as influenza viruses do, but they do mutate over time. The variants generally produce the same range of symptoms as the original strain of the coronavirus. But the mutations may help the virus spread more effectively from person to person, or have an advantage in sneaking past either natural or vaccine immunity.

What variants were already circulating in the United States?

To date, public health officials have noted five “variants of concern,” plus two “variants of interest” not yet considered as worrisome. So far, no variants have emerged that fit the most worrisome of the three official categories — “variants of high consequence.”

The World Health Organization decided early this year to name the variants after Greek letters, both to simplify the discussion and to limit the stigma of having a variant named for a country.

The first four “variants of concern” — alpha, beta, gamma and delta — have been circulating in the United States for most of this year. But the most dominant variant has been delta, due to its ability to spread from person to person more quickly than other variants. For months, delta has accounted for more than 99% of coronavirus infections in the U.S.

There were no confirmed cases of omicron in the United States as of midday Nov. 29, but experts warn it's just a matter of time. It could be in the U.S. already, merely undetected.

How did omicron emerge?

Though scientists aren't sure precisely where omicron first surfaced, it was most likely in a southern African nation.

Experts say low vaccination rates in that part of the world probably played a role in creating a favorable environment for the mutations that produced omicron. (It can be pronounced either AH-mi-crahn or OH-mi-crahn.)

"Many countries in Africa have populations with very low immunity — about 30% in South Africa are vaccinated," Smith said. "In a largely non-immune population, the virus can sweep through, and each new person infected is a chance for the virus to mutate."

Why did public health officials react so urgently to omicron?

The concern stems from the scope and nature of the new variant's mutations. South African health officials noted 50 notable mutations, 30 of which are on the spike protein, a key structure in the virus, New York magazine reported. That's more than previous variants have had.

"If we were looking out for mutations that do affect transmissibility, it's got all of them," University of Oxford evolutionary biologist Aris Katzourakis told Science magazine.

Still, what's uncertain at this point is how effectively those mutations will work together in creating a variant that can consistently outcompete delta.

What do we know about omicron's degree of infectiousness?

The omicron variant is so new that scientists are just beginning to learn about its characteristics. Because of this, experts urge caution in drawing conclusions, especially from anecdotal evidence.

That said, scientists say they would not be shocked if omicron becomes as easily transmissible as delta.

"The answer is uncertain, of course, but it looks as though it will be at least as infectious as delta," said Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University School of Medicine.

One complicating factor, Schaffner said, is that the initial areas of fastest spread have been in areas of Johannesburg populated by young adults and college students, who tend to have lower vaccination rates. The vulnerability of these groups to infection may be exaggerating how rapidly omicron seems to be spreading.

What do we know about whether omicron makes patients sicker?

The early evidence is somewhat conflicting, but there are signs that symptoms from omicron may not be more severe than previous variants. Dr. Angelique Coetzee, who chairs the South African Medical Association, has said that the early cases being seen among the unvaccinated are mild.

It remains to be seen, however, whether older and unhealthier patients will also see milder symptoms. Another caveat is that it may be too early in omicron's spread to see cases that have seriously progressed.

Will existing vaccines be effective against the omicron variant?

Scientists are cautiously optimistic that existing vaccines will also be effective against omicron, just as they have been against delta, at least in being able to prevent illness severe enough to require hospitalization.

"Scientists in South Africa and Israel, where the variant has also been detected, have indicated that they are not seeing severe disease among the vaccinated," Gandhi said.

Gandhi added that the immunity-providing B cells produced by the vaccines have been shown to produce antibodies against variants, and that T-cell immunity, which protects against severe disease, is robust and should not be at risk from the mutations being seen in omicron. The vaccines also produce polyclonal antibodies that work against multiple parts of the spike protein, she said. Finally, booster shots have been shown to be effective in strengthening immunity quickly.

"Most scientists believe we should still have protection against severe disease with vaccinations, and vaccination remains the mainstay of control," Gandhi said.

Bottom line: If you haven't been vaccinated, and especially if you haven't had the disease yet, get vaccinated. And if you've already been vaccinated, get a booster.

How long will it be before we have a better handle on the threat from omicron?

Moderna, Pfizer-BioNTech and Johnson & Johnson are all testing the effectiveness of their existing vaccines against omicron in the lab, based on variant-analysis protocols developed early this year. Those results should be available in a week or two.

Other questions — including whether omicron makes you sicker, and whether it's more transmissible — will take longer to answer because they require careful contact tracing and accurate diagnoses of those infected.

To better answer those questions, Smith said, "I think, at a minimum, it will take a month to get some preliminary data, and quite possibly longer to really know the fuller picture. We also won't know about real-world experience in vaccine breakthroughs until that time."

Can we expect a specific new booster to be developed for omicron?

It's unknown whether the omicron variant will require a reformulated booster. A newly formulated booster wasn't necessary for delta, because researchers determined that the existing formulation was still effective.

That said, vaccine makers can jump in with a new booster quickly if they have to.

In the event that such a variant emerges, Pfizer and BioNTech "expect to be able to develop and produce a tailor-made vaccine against that variant" within 100 days, pending regulatory approval, a Pfizer spokesperson told The Washington Post.

Dr. Matthew Laurens, a specialist in pediatric infectious diseases at the University of Maryland School of Medicine, said he's confident boosters could be developed and tested quickly if needed, "likely within a few months."

What happened to the other variants?

Between May 2021, when delta was named a variant of concern, and November 2021, when omicron was given the same label, two other variants were elevated to the lower "variant of interest" status: lambda from Peru and mu from Colombia. Other variants, such as one discovered in Nepal called "delta-plus," attracted notice during that period as well. But none of these managed to outcompete delta in a consistent way, so they were never elevated to "variant of concern."

This is the most hopeful outcome for omicron. The other variants "all had similar concerns around them, but they didn't expand to any significant degree after the initial reporting," Gandhi said.

Is it reasonable to think the u.s. is in a better position to handle omicron than it was for delta?

Experts generally agreed that the United States should be better prepared to battle omicron than it was when delta emerged earlier this year.

"We are in a much better position since we have higher rates of vaccination, the availability of boosters for everyone over 18 and vaccine eligibility down to 5 years old," Gandhi said. "We also have higher rates of natural immunity in this country due to the delta variant's spread since July 2021. And we have oral antiviral therapeutics on the horizon. So we have the tools to fight this new variant."

The challenge, Schaffner said, will be to make sure Americans continue to get vaccinated and boosted, and to make use of testing and maintain safe behavior in public.

"All these tools are available," he said. "The big question is how inclined the general public is to use these tools."

Is the coronavirus going to be around permanently, like the flu?

Experts now believe it's unlikely that the coronavirus will either be eradicated from the globe, like smallpox has been, or even eliminated in the United States, as polio was following near-universal vaccination. The combination of rapid mutations and too-low vaccination rates make it likely that covid-19 won't follow smallpox and polio into submission.

"This will more likely be the influenza model, where we have to track mutations annually and alter the boosters accordingly," Schaffner said. In fact, he said, efforts to create combined coronavirus-flu shots are already underway.