The Omicron variant: What we know so far

On Nov. 26, the World Health Organization (WHO) named a new coronavirus variant "Omicron" and designated it as a "variant of concern."

But what makes this SARS-CoV-2 variant different and why are scientists worried about it? Because the variant has only been recently identified, there's a lot we don't know about it.

Scientists are concerned that Omicron has a very high number of mutations, many of them in genes that code for the spike protein, which the coronavirus uses to latch onto and invade human cells. Early evidence suggests that people who previously recovered from COVID-19 may have a higher risk of reinfection with Omicron compared with prior variants, according to a statement from the WHO.

But it's not yet clear how severe or transmissible Omicron is, nor is it clear how current COVID-19 vaccines will fare against it. Experts say it's likely that the vaccines will be less effective due to these mutations, but they will likely still confer some protection. From its origin to its likely impact, here's everything we know so far about Omicron.

Origin

Officials in South Africa first reported Omicron (B.1.1.529) to the WHO on Nov. 24, following a sharp increase in cases in Gauteng province in the previous weeks. The first known and confirmed infection with Omicron was from a sample taken on Nov. 9, and now, the number of Omicron cases is rising across South Africa, according to a WHO statement.

Though South Africa was the first to report Omicron to the WHO, it's not clear what country the variant emerged from, according to NPR. Many countries have since put travel bans on many southern African countries including South Africa. "There is very little utility of these kinds of bans," Saad Omer, director of the Yale Institute of Global Health, told NPR. Omicron has also been detected in Canada, Austria, Belgium, Denmark, England, France, Germany, Italy, The Netherlands, Portugal, Scotland, Botswana, Israel, Australia and Hong Kong, according to The Washington Post.

Common PCR tests can detect the Omicron variant and easily distinguish it from other variants due to a mutation in one of the three genes that the test targets. "Using this approach, this variant has been detected at faster rates than previous surges in infection," according to the WHO.

Mutations

Omicron has more than 30 mutations in the genes that code for the spike protein, according to Nature. Of these mutations, 10 are in the "receptor binding domain," or the part of the spike protein that latches onto human cells, according to The Guardian.

Meanwhile, other mutations, some of which were previously found in past variants, are "concerning" and could be linked to higher transmissibility or could help the virus evade immune defenses, according to a technical brief released by the WHO on Nov. 28.

"The likelihood of potential further spread of Omicron at the global level is high," according to the brief.

Severity

It's not yet known whether Omicron causes more severe disease compared with previous variants.

Early evidence suggests hospitalization rates are increasing in South Africa, "but this may be due to increasing overall numbers of people becoming infected, rather than a result of specific infection with Omicron," according to the WHO. Only about 24% of South Africa's population is fully vaccinated against COVID-19, according to Our World in Data.

The first reported infections in South Africa were in university students, who are "younger individuals who tend to have more mild disease." However, only about 6% of the population of South Africa is older than the age of 65, according to the Telegraph. So it's unclear whether the variant will cause more severe disease in those who are at increased risk, such as older people.

No solid evidence suggests that symptoms of Omicron differ from those of previous variants, according to the WHO.

But Dr. Angelique Coetzee, a private practitioner and chair of South African Medical Association, told the BBC that the patients she's seen so far with the new variant have had "extremely" mild symptoms.

Of the few dozen patients she's seen recently who tested positive for COVID-19, most were healthy young men who turned up "feeling so tired," Coetzee told the Telegraph. None of her patients had loss of taste or smell, and none needed to be hospitalized, according to the BBC.

However, these early anecdotal reports can be misleading and it's still too early to say whether Omicron causes milder or more severe disease than earlier variants.

Transmissibility

It's not yet clear if Omicron spreads more easily from person to person compared with previous variants.

The number of people in South Africa who have been testing positive for COVID-19 has increased in areas battling Omicron, but it's not yet clear if the rise can be explained by the spread of the new variant or other factors, according to the WHO.

Vaccine effectiveness

It's also not known how effective current COVID-19 vaccines will be against Omicron.

Most COVID-19 vaccines, including those used in the U.S., prime the immune system specifically against the spike protein. Because Omicron has many mutations in the spike protein, experts are worried that current vaccines may be less effective at training the immune system to recognize it.

"Based on lots of work people have done on other variants and other mutations, we can be pretty confident these mutations are going to cause an appreciable drop in antibody neutralization," or the ability of antibodies to attach to the viruses and stop them from invading human cells, Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle, told the New York Times.

But experts told The Guardian that while vaccines may be somewhat less effective against Omicron compared with previous variants, they will probably still confer some protection.

"I think a blunting rather than a complete loss [of immunity] is the most likely outcome," Paul Morgan, an immunologist at Cardiff University told the Guardian."While some of the antibodies and T cell clones made against earlier versions of the virus, or against the vaccines may not be effective, there will be others, which will remain effective."

What's more, T cells, or immune cells that attack virus-infected cells, may be more "impervious" to differences among variants compared with antibodies, Danny Altmann, professor of immunology at Imperial College London told The Guardian.