Main content
What we've learned about the Omicron variant

Media Contact

Gana Ahn

Just weeks after its discovery, the Omicron variant of COVID-19 has been identified in 30 countries, including the United States. Researchers around the world are swiftly sharing what they have learned about Omicron, but much about the variant remains unknown. 

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, teamed up to discuss the latest news about the Omicron variant and how we can prepare for a potential wave of new infections. 

Their conversation follows previous discussions of Omicron and is part of an online video series hosted by Guest, who also leads the Emory COVID-19 Outbreak Response Team. Watch the full conversation between Guest and del Rio here.

Q: Is Omicron more infectious than previous variants such as Delta? 

A: Early data indicate that the Omicron variant is highly infectious, and potentially twice as transmissible as Delta. 

“Omicron cases seem to be doubling every three to four days,” says Guest. If this trend continues, Omicron may overtake Delta as the dominant strain by mid-January. 

“It looks like, at least in household context, there’s about a threefold higher transmission rate than that of Delta,” says del Rio. “Lots of infections, lots of transmission, therefore [could lead to Omicron] becoming the dominant variant throughout the country in a very short period of time.” 

Q: How can we prepare for potential waves of Omicron in the coming months? 

A: “The timing on this is not very good,” Guest says. “For the first time in several months in the U.S., cases, hospitalizations and deaths are again increasing, and this is before Omicron has become the predominant variant in the U.S.” 

“On Dec. 13, there were more cases of COVID-19 in the U.S. than at any point in time during the peak of the Delta wave,” she continues. “Yesterday, almost 1,400 people died of COVID-19 in the U.S.” 

“We have to emphasize that Delta is driving the increasing cases, hospitalizations and deaths,” del Rio says, “primarily in northern states and primarily among unvaccinated individuals. So, vaccination continues to be our number one strategy.” 

More than 60% of Americans are fully vaccinated. Guest and del Rio emphasize that unvaccinated individuals should begin their primary vaccination series as soon as possible to protect themselves and their communities from the risk of severe disease. 

Vaccinated individuals who are 18 years of age and older — especially those at high risk for severe disease due to COVID-19 — should receive booster shots. People who received a primary series of Pfizer or Moderna vaccines should receive a booster six months after the second dose. Johnson & Johnson vaccine recipients should receive a booster two months after the single dose. 

“Getting boosted increases your level of protection,” del Rio explains. “People say, ‘How do I prepare for Omicron?’ I say, ‘Get boosted.’” 

Q: What role does COVID-19 testing play in preventing the spread of Omicron? 

A: “Testing is incredibly important as we move forward,” Guest says, noting that participation in her COVID-19 testing events has dwindled. “Hopefully, that means some people have moved to testing at home, but we want to reiterate that testing is important to stop the spread of COVID-19.” 

Before gathering for the holidays, del Rio suggests that all attendees get tested for COVID-19. “And it really matters who is going to be in your household. If I have my 97-year-old mother there, we need to be sure everybody is uninfected,” he says. “If you’re going to be around people who are high-risk, you really want to get tested.” 

“It’s important that we realize that these tests are not perfect, so ideally you want to get tested 24 hours before the event and again right before the event,” del Rio adds. At-home COVID-19 tests available at drugstores provide two tests per package to encourage repeat testing. “You should test yourself twice, and by doing that you dramatically increase the predictive value of the test.” 

Q: Does Omicron cause more severe disease than the Delta variant? 

A: “Looking at some of the data, mostly from South Africa, it’s not yet totally clear whether infection from Omicron causes more severe disease compared to infections with other variants,” Guest says.  

Anecdotal data from South Africa indicate that hospitalization rates with the Omicron variant are lower than with previous strains, and that patients admitted to the hospital experience milder disease and shorter stays. 

Although hospitalization rates appear lower, many of the individuals infected with Omicron in South Africa are young people who typically experience mild illness from COVID-19. There are also many cases among travelers, who tend to be generally healthy as well. 

“Currently, even with all the progress that has been made, we know more about what we don’t know than what we do know about Omicron,” del Rio says. For example, there is not yet enough data to predict whether the Omicron variant may have a more severe impact if it spreads through a high-risk population such as a nursing home. Residents at nursing homes and long-term care facilities can prepare for potential waves of Omicron by getting vaccinated and receiving booster shots. 

“Even if it produces very mild disease, if it infects a lot of people, it’s going to end up in a lot of hospitalizations,” del Rio adds. “If you’ve got 100,000 infected individuals and the hospitalization rate is 2%, that’s 2,000 people ending up in the hospital. You can see a lot of hospitalizations just by the sheer numbers. So, limiting transmission still continues to be critically important.” 

Q: Do COVID-19 vaccines work against Omicron? 

A: “The Omicron variant does seem to be able to partially evade vaccine protection,” Guest says, citing early data from a South African study suggesting that the Omicron variant poses a higher risk of breakthrough infections than other strains. 

Eight recent lab studies also indicate that Omicron significantly reduces the number of neutralizing antibodies from a complete mRNA vaccination series. “But it’s really important to note that reduction in neutralizing antibodies is not the same thing as reduction in vaccine effectiveness,” Guest adds. 

“Lab data is not the same as clinical data,” del Rio says. “What we are seeing right now are results from eight studies, in which we’re looking at ability to neutralize the virus with vaccines in laboratory samples. That efficacy is going to be very different than in real clinical samples, and that is because immunity is a lot more than antibodies.” 

Guest notes that recent studies suggest T cells, the immune system’s second line of defense, continue to work very well against the Omicron variant.   

“We now need to see what happens in the clinic, but I am afraid that the current vaccines are not as good against the Omicron strain as they were against prior strains, even if you get boosted,” del Rio continues. “If you want to have the best protection possible, get boosted, but understand that it’s not sufficient. Therefore, masking and other measures continue to be important.” 

Q: Do COVID-19 treatments work against Omicron? 

A: “Currently available monoclonal antibodies — primarily the Regeneron monoclonal antibodies that we have relied upon a lot, because it was very effective in patients with Delta infection — have essentially no activity against Omicron,” del Rio says. “I do worry if some of our treatments are being importantly impacted by this new variant.” 

Oral antiviral pill treatments, such as molnupiravir and paxlovid, do appear effective against Omicron, but they are not yet authorized for use in the U.S.  

“The government has bought millions of doses of both medications. Hopefully we will have them available, because having drugs that we can give to people will be critically important,” del Rio says. “Not only do they prevent the risk of severe disease and hospitalization — they also decrease the viral load in individuals, and by doing so, they decrease the possibility of transmission.” 

Q: With the spread of Omicron, will the definition of “fully vaccinated” change to include boosters? 

A: The Centers for Disease Control and Prevention currently considers a person fully vaccinated against COVID-19 two weeks after a second dose of mRNA vaccine (Pfizer or Moderna) or two weeks after a single dose of Johnson & Johnson vaccine.  

“Do I think that the definition of fully vaccinated should include a third shot? Yes, I think so,” del Rio says. “At this point in time, what I am doing myself — what I’m telling my relatives, my family and my patients — is that full vaccination includes three doses” of mRNA vaccine, or at least one mRNA booster dose. 

Q: Does immunity from a previous COVID-19 infection protect against Omicron? 

A: Even if previously infected with COVID-19, unvaccinated individuals likely have no protection against the Omicron variant. 

“A study published over the weekend showed that neutralizing antibodies among people previously infected with Alpha, Beta or Delta who were not vaccinated completely failed to protect against Omicron,” Guest says. “Those who were infected and vaccinated, in either order — infection and then vaccination or vaccination and then a breakthrough infection — had a very strong response to Omicron. These data seem to clearly show that we do not want to chance fighting Omicron by counting on a previous infection to protect us.” 

“Post-infection immunity provides some level of protection against Delta. It provides no protection against Omicron,” del Rio stresses. “What I tell people that are still using infection as a mode of protection is: get vaccinated. Get at least one dose of vaccine, because then you’ll be super-immune.” 

Q: Is it still necessary to wear a mask? 

A: “I wear my mask when I’m in public spaces and when I’m with a lot of people,” del Rio says. “Unfortunately, the reality is when we get together in small groups — when we get together in a household, with families — we are not wearing a mask.”  

For this reason, del Rio recommends postponing gatherings with unvaccinated friends or relatives. “In a very polite way, you need to say, ‘I’m sorry, but we probably don’t want to get together this holiday season. We can Zoom you in, or you can wear a mask the whole time.’” 

Both experts emphasize that COVID-19 vaccinations, boosters and testing can help create a safe environment for family gatherings, even with the spread of Omicron.  

“We can get together safely for the holidays, but we need to do it by taking additional precautions,” del Rio says. 

“Please keep doing the things that we know will protect you from COVID-19 and will keep your community and family members safe,” Guest adds.