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What we know, and don't know, about the Omicron variant

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Jill Wu

As COVID-19 continues to spread at a fast rate, new variants of the virus have emerged around the world. The dominant strain in the U.S. is currently the highly contagious Delta variant, which accounts for more than 99% of identified cases.

In some parts of the world, a newly discovered variant called Omicron is beginning to spread rapidly. On Nov. 26, the World Health Organization (WHO) classified Omicron as a “variant of concern.”

Much remains unknown about the transmissibility of Omicron and the severity of symptoms it may cause. Jodie Guest, PhD, professor and vice chair of the department of epidemiology at Rollins School of Public Health, and Carlos del Rio, MD, distinguished professor of medicine, epidemiology and global health and executive associate dean of Emory University School of Medicine at Grady Health System, sat down to answer questions about what we know and still need to learn about this new variant. 

Their conversation is part of an online video series hosted by Guest, who also leads the Emory COVID-19 Outbreak Response Team, answering questions related to the COVID-19 pandemic. Watch the full conversation between Guest and del Rio here.

Q: What is the Omicron variant?

A: Omicron is the name of the B. variant of COVID-19, first reported to the WHO from South Africa. The WHO classified Omicron as a variant of concern on Nov. 26.

“The decision to name this as a variant of concern was based on the evidence that Omicron has several mutations that may impact how it behaves, specifically on how easily it spreads and on the severity of illness it might cause,” says Guest. “I want to emphasize the word ‘may.’ There is a lot that we still do not know about this variant.”

Health officials around the world are currently identifying and tracking cases of the Omicron variant. “Based on the spread across countries, we can feel certain that it is spreading in more communities than we currently have identified,” Guest says.

Q: How do virus mutations play a role?

A: “Respiratory viruses, primarily RNA viruses, tend to mutate,” says del Rio. “They mutate when they’re reproducing; they’re mutating when they’re transmitting. And variants have changed the end game of this pandemic. This is not the first variant to emerge, nor is it the last one.”

The dominant variant in the U.S. is currently the Delta variant, which can cause more severe illness than previous strains and is more than twice as infectious. It is not yet known whether the Omicron variant is more contagious or causes more severe symptoms.

“Omicron has multiple mutations, and those mutations occur in two sites in particular,” del Rio explains. “One of them occurs in the spike protein, and this is really important because that is where a lot of our treatments, our antibodies, our vaccines are directed.” The other mutation occurs in the receptor-binding domain, a mutation del Rio says could be “associated with increased transmissibility.”

“That’s why scientists are increasingly alarmed by this strain, because it does appear to have a lot of those things that make us worry; however, at this point in time, there’s many things that we don’t know,” he says, adding that studies are currently underway to answer these questions.

Q: Did Omicron originate in one person?

A: “There is some conversation this mutation may have happened in one immunocompromised person, and not a mutation from the Delta variant spreading wildly,” Guest says. “This is another reason that we want to make sure everyone gets vaccinated, so that the virus does not have a place to mutate.”

“We know that immunosuppressed individuals who get infected can be infected for very long periods of time, and when they don’t clear the virus as quickly, the virus survives in that individual by mutating,” del Rio says. “We are very concerned that immunosuppressed individuals could potentially be how these variants are being developed, so it is critically important that those immunosuppressed individuals get their immune systems reconstituted — for example, people with HIV get an antiretroviral therapy — then they respond to the vaccine like anybody else.”

For individuals such as transplant recipients whose immune systems do not respond to vaccination, del Rio notes that scientists are developing treatments to help them clear the virus if infected. He also emphasizes the continued importance of transmission mitigation measures: “Masking, social distancing, handwashing — all those things that we talk about over and over are very effective strategies to prevent you from getting infected.”

Q: Is Omicron more contagious than Delta?

A: Further study is needed to determine whether the Omicron variant is more transmissible than previous variants. Health officials have reported rapid spread of Omicron in South Africa, but del Rio notes that the country previously had very low rates of COVID-19 transmission.

“When we say, ‘spread rapidly,’ it means that South Africa went from having 300 cases a day to having 4,000 cases a day. Still much, much lower than what we’re seeing in our country, for example,” he says.

Like many countries, South Africa also has a low vaccination rate despite vaccine availability. “Vaccine hesitancy is a global issue,” del Rio emphasizes. “Had this variant come in a highly vaccinated state, we may see a very different presentation.”

Q: How important is COVID-19 testing?

A: Testing is crucial to prevent the spread of COVID-19 and variants such as Omicron. As more people travel for the holidays, both Guest and del Rio recommend following a testing regimen.

“I think you can probably get tested 72 hours before you get on a flight and then get tested a day or two after you arrive to your destination,” del Rio says. “You will be able to catch if you were infected and asymptomatic, and you will then be able to prevent transmitting to others.”

It is also important to get tested before gathering in public indoor spaces. “People are getting infected when they gather in large groups indoors, in poorly ventilated sites. If you’re going to go to a bar with friends, get tested before you do that. If you’re going to go to a restaurant, get tested before you do that,” del Rio says. “It’s a simple strategy to pick up disease, and I think testing needs to be ramped up significantly.”

“Vaccination offers many advantages, but testing is also incredibly important to stop the spread of infection, detect it early, and know when we need to get someone to monoclonal antibodies, or perhaps one of our newer antiviral pills once they become available,” Guest adds.

Q: Does Omicron cause more severe disease?

A: “It’s not yet clear whether infection from Omicron causes more severe disease compared to infections with other variants,” Guest says. “Initial reports of infections in South Africa were among university students, and we know that younger individuals often — not always, but often — have more mild disease.”

“We don’t have enough information yet. There’s simply too few cases studied,” del Rio adds.

Q: Are COVID-19 vaccines effective against Omicron?

A: All COVID-19 vaccines available in the U.S. are effective, even against the Delta variant, Guest says. 

del Rio has spoken to vaccine specialists who say the COVID-19 vaccines will likely be as effective against Omicron as they are against Delta. “And even if the efficacy goes down a little bit, if you get boosted, the efficacy is rapidly recovered,” he says.

“There’s a study from Israel showing that after you boosted individuals, the chance of getting infected decreases tenfold and the chance of getting severely ill or hospitalized decreases close to twentyfold,” del Rio continues. “I want to remind everybody: go get your booster.” In the U.S., individuals ages 18 and older are eligible for COVID-19 vaccine boosters.

del Rio adds that people who have received COVID-19 booster shots are more likely to have mild or asymptomatic cases of COVID-19 if they do get infected.  “You’re not going to end up in the hospital. Again, the goal of vaccine is to prevent severe disease and death.”

“Keep doing the things that we know protect each of you and protect those around you,” Guest says. “Get vaccinated if you’re not vaccinated yet, please get boosted if you’re already vaccinated, continue to wear your mask indoors in public spaces, stay in well-ventilated spaces and please use testing to make sure we stop the spread of COVID-19.”

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