How Omicron Stacks Up Against the Delta Variant—Including Whether or Not We'll Need a New Vaccine

·7 min read
Photo credit: nopparit - Getty Images
Photo credit: nopparit - Getty Images

The Omicron variant has dominated headlines ever since the World Health Organization (WHO) designated it a COVID-19 variant of concern last week.

With that, it’s only natural to wonder how Omicron compares to the Delta variant, which has been the main variant in the U.S.—and many parts of the world—for months now. In the U.S., Delta currently is responsible for 99.9% of COVID-19 cases, per data from the Centers for Disease Control and Prevention (CDC). However, experts say that Omicron has a few key mutations that could potentially make it able to outcompete Delta.

A rapid rise in COVID cases in South Africa, where Omicron was first detected, happened to coincide with the detection of the new variant, the WHO said in a statement last week, which also suggests Omicron may be able to unseat Delta as the main COVID-19 variant.

While there’s a lot we still don’t know yet about Omicron, there is some information out there that suggests this isn’t a variant to write off—just like Delta. Here’s what you need to know about Omicron vs. Delta.

Omicron vs. Delta

Both Omicron and Delta are variants of the original SARS-CoV-2, the virus that causes COVID-19. “Every time this virus enters a new person, it multiples millions of times. That gives it the opportunity to mutate,” explains William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. “When that happens, occasionally you get a variant.”

Most variants are dead-end mutations, meaning they don’t end up doing much, Dr. Schaffner says. “But every once in a while you get a mutation or a whole series of mutations that change the character of the virus,” he says. “It’s like discovering you have a new cousin. You can see it’s related to your family but it has its own personality and characteristics.”

The Delta variant is more than twice as contagious as previous COVID-19 variants, according to the CDC, and it may cause more severe illness than previous variants in unvaccinated people.

The Omicron variant has a “large number of mutations,” per the WHO, and it seems to be more likely to reinfect people who have previously had COVID-19. “Many of those mutations involve the actual spike protein, which is the critical part of the virus that allows it to enter the cells of our body and make us sick,” Dr. Schaffner says. What’s unclear right now, though, is whether Omicron is as contagious as Delta or even more infectious than Delta.

Is Omicron worse than Delta?

“The short answer is, we don’t know,” says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. However, he points out, Omicron has a large number of mutations on its spike protein which, again, is what SARS-CoV-2 uses to infect your cells. “The reason people are nervous is because of those mutations,” he says. “But are the mutations setting things up to go in a bad direction or will they cancel each other out? We just don’t know yet.”

Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security, agrees. “Omicron has some unique mutations and other mutations that were found in other variants, but not in Delta,” he says. “There's not enough information to say whether this variant is worse than Delta. It may be that both are handled by our vaccines when it comes to preventing serious illness.”

Symptoms of Delta vs. Omicron

In general, symptoms of COVID-19 have remained fairly steady, regardless of variants. Per the CDC, those include:

  • Fever or chills

  • Cough

  • Shortness of breath or difficulty breathing

  • Fatigue

  • Muscle or body aches

  • Headache

  • New loss of taste or smell

  • Sore throat

  • Congestion or runny nose

  • Nausea or vomiting

  • Diarrhea

Data on Omicron is still very preliminary, but one doctor who has treated Omicron patients told the BBC that people have experienced “extremely mild symptoms” with the variant so far. She also noted that the symptoms have been a little different from other strains of COVID-19.

“It actually started with a male patient who’s around the age of 33 ... and he said to me that he’s just [been] extremely tired for the past few days and he’s got these body aches and pains with a bit of a headache,” Angelique Coetzee, M.D., chair of the South African Medical Association, told the BBC.

The patient had a “scratchy throat” but no cough or loss of taste and smell. Dr. Coetzee said she tested the man for COVID-19, along with his family—all were positive. She also saw more patients that day that had similar symptoms.

“What we are seeing clinically in South Africa—and remember I’m at the epicenter of this where I’m practicing—is extremely mild, for us [these are] mild cases. We haven’t admitted anyone, I’ve spoken to other colleagues of mine and they give the same picture,” she said.

But Dr. Coetzee noted that the patients she had seen were mostly young and otherwise healthy people. “Before we can judge the clinical spectrum of illness, it is important to get a bigger sample size, including those who are at higher risk for severe disease,” Dr. Adalja says. “But it is reassuring that those that are being hospitalized tend to be unvaccinated.”

Still, he says, “there is not enough clinical data to be able to say anything definitive about how symptoms may differ with this variant. But I suspect they will all still be in the same range.”

Are the current COVID vaccines effective against Omicron?

This is also a huge question mark. “Omicron shares similar mutations to the Beta and Gamma variants, which are more resistant to vaccination,” Dr. Russo says. That’s potentially concerning, he says, and may be why Moderna’s CEO predicted to the Financial Times that the existing vaccines may not be as effective against Omicron.

“There is no world, I think, where [the effectiveness] is the same level...we had with [the] Delta [variant],” Moderna CEO Stéphane Bancel said. Bancel also predicted that there will be a “material drop” in efficacy. “I just don't know how much because we need to wait for the data,” he said. “But all the scientists I've talked to...are like, ‘This is not going to be good.’”

That said, there are low COVID-19 vaccination rates in South Africa and Omicron cases seem to be largely in people who have not gotten the vaccine. Getting your booster dose, which the CDC now recommends all Americans over the age of 18 get, should help, Dr. Russo says. “Booster shots give you a 10-fold increase in neutralizing antibodies,” he says. “Will that buffer be enough so that we’ll still have a significant degree of protection? We don’t know yet.”

Dr. Adalja says, however, that Omicron may be able to evade the vaccine on some level. “Of all the variants, this is the one that seems to come closest to the threshold for a need for a reformulation [of the vaccine]—if it spreads more widely and causes a problem,” he says.

New COVID-19 vaccines are already in development

It's unclear at this point if they'll be needed, but COVID-19 vaccine makers say they're already working on vaccines that would specifically target Omicron. Moderna's Chief Medical Officer Paul Burton told NBC News that his company has already started work on this, and Pfizer and BioNTech said they could develop a vaccine that targeted Omicron-within six weeks. Initial batches would be available to ship initial batches within 100 days if needed, the companies said.

Johnson & Johnson also said in a press release that it can create an Omicron-specific vaccine if needed.

But, with all of the news around Omicron, doctors stress that there are a lot of unknowns, including whether Omicron will spread more widely or fizzle out.

“At the end of the day, I think we’re going to be OK,” Dr. Russo says. “I don’t think the sky is falling just yet.”

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