Yes, omicron has overtaken delta. No, it's not March 2020. – USA TODAY

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Although details about the omicron variant are still sketchy, a picture is starting to emerge – and it’s not all bad news.
As the omicron variant sweeps across the world and pushes out the delta variant that preceded it, scientists are rushing to understand how it might change the coronavirus pandemic, now entering its third year.
So far, it’s clear that omicron is highly contagious – roughly twice as contagious as delta and four times more than the original virus.
Experts worry that even if it’s less virulent, which isn’t yet clear, it could still cause enough hospitalizations to overwhelm health care systems here and abroad.
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But this is not 2020. Back then, only a handful of people on Earth had been exposed to the SARS-CoV-2 virus that causes COVID-19. Everyone’s immune system was unprepared.
Today, the vast majority of Americans have either contracted COVID-19 or been vaccinated once, twice or three times against it. That should – though there are still no hard numbers to confirm it – provide people protection against severe disease and death.
“I think we should reassure people that if they’ve been vaccinated with two doses or naturally infected, they’re likely protected against serious illness,” said Dr. Paul Offit, a pediatric infectious disease expert and director of the Vaccine Education Center at Children’s Hospital of Philadelphia.
What’s not clear is how people who have never been vaccinated or contracted COVID-19, or whose protection has waned significantly over time, will fare if they catch omicron.
An experiment in hamsters, which should see results as soon as Tuesday, will provide the first indication of how people far from an infection or vaccination may fare if they are infected, said Galit Alter, an immunologist and virologist at Harvard Medical School and the Ragon Institute of MGH, MIT, and Harvard.
More previously vaccinated or infected people are contracting omicron than with earlier variants, data shows. But vaccinated people, and perhaps those who’ve already been infected, are probably less likely to pass the virus to others.
It’s still the unvaccinated and unprotected who are providing opportunity for the pandemic to continue, Offit said.
“You have a critical percentage of the population who are unvaccinated and shedding this virus,” he said. 
Data out of South Africa, where omicron hit early and which has tracked cases carefully, are still incomplete but encouraging. 
There, hospitalization rates are much lower than in previous waves of infection, and the people hospitalized are not as sick as those infected with the beta or delta variants, said Salim Abdool Karim, a South African epidemiologist and infectious diseases specialist, and member of the Massachusetts Consortium on Pathogen Readiness.
Only about 2% to 4% of infected people are ending up in hospitals this time, compared to about 20% during the previous beta and delta waves, Karim said. Before, two-thirds of those hospitalized were considered to have severe cases; now only about one-quarter meet that criteria. Death rates are one-tenth as high as they were with previous variants.
“The clinical picture we are seeing is one of substantially less severe disease,” he said.
Karim said he doesn’t yet have information on how many hospitalized patients had been previously infected or vaccinated, though he expects to get that soon.
Anecdotally, Karim said, “there’s a preponderance of unvaccinated” in hospitals, likelyabout 75% of patients. “Is it more severe in that group? What’s the picture? I can’t tell at this point because I don’t have that data.”
The department of public health in South Africa recently decided people exposed to an infected person but not yet infected themselves do not have to quarantine. 
Karim said he recommended his government reinstitute mandates to minimize crowds. Officials didn’t take his advice. But the general public has followed with their feet.
“Theaters are empty. Restaurants are half-empty with just a handful of people,” he said. “People have come to that conclusion themselves … Indoor gatherings? No. No.”
Without question, omicron is more contagious than other variants, he said, with about 35,000 to 45,000 cases in South Africa in the first month of the beta and delta waves and 133,000 cases in the first month with omicron.
Other countries like Denmark have seen similarly high rates of transmissibility and low rates of serious disease.
But unlike other variants, which slowly made their way from country to country, omicron is exploding around the world simultaneously, said Dr. Jacob Lemieux, an infectious diseases staff physician at Massachusetts General Hospital.
“In prior waves, we had a few weeks to watch what was happening in western Europe and other places to know what we were in store for,” he said. Not this time. “We’re not going to have the luxury of watching what’s going to unfold in our country elsewhere in advance.”
Although it’s still early days in the American experience with omicron, the variant has already overtaken delta in the U.S. Modeling shows as of Saturday, the omicron variant accounted for 73.2 % of new COVID-19 infections in the nation, the Centers for Disease Control and Prevention reported, up from 12.6 % the previous week.
“It’s clear we’re now waist-deep in the omicron wave,” Lemieux said. “The question is how severe is it going to be?”
It may follow South Africa’s pattern with the vast majority of people getting nothing worse than a bad head cold. Or it may cause more hospitalizations here, particularly among those who have waning or no protection, potentially overwhelming the health care system, which was already dealing with a wave of delta infections, he said.  
At Texas Children’s Hospital, they’re still waiting to confirm how many cases are omicron versus delta, but pediatric COVID-19 hospitalization rates have more than doubled in just four days, with the number of patients now in the double-digits. 
The rate of positive tests also jumped from well below 5% five days ago to 15% Monday, according to James Versalovic, co-chair of the Texas Children’s Hospital COVID-19 Command and the hospital’s pathologist-in-chief.
“These are signals that tell us we have a surge beginning,” Versalovic said. “Every indication now is pointing in the same direction.”
It’s not yet clear whether children will react differently to omicron than they did to delta. Nor does the hospital yet know the vaccination status of the children over 5 (vaccinations are not yet authorized for those younger than 5), their parents’ vaccination status, or whether any of the children was previously infected with COVID-19, he said. 
Dr. Eric Topol, of the Scripps Research Translational Institute, said he’s hearing anecdotal descriptions that omicron infections differ from delta. People appear to not be losing their smell or taste the way they did with earlier variants.
If true, that would be extremely good news, Topol said, because it would mean this variant isn’t entering the brain and would take off the table the potential risk of neurological problems in the future.
Omicron also appears not to get into the lung cells, according to two studies from Hong Kong and the U.K. “That was the most distinguishing feature (of COVID-19) until now,” Topol said, and the reason it caused so much lung damage. “I know of a few people who had really high fevers (with omicron),” he said. “No one’s had pneumonia.”
What will happen with the virus in the future, of course, remains uncertain. 
“The virology community is kind of split 50-50 on whether this creature has big surprises in store for us or whether we’ve seen most of what it can do,” Dr. Jeremy Luban, another member of the Massachusetts Consortium on Pathogen Readiness, said on Monday’s call.
He and others were surprised to see how many differences omicron has from its predecessor variants – without any obvious intermediate changes. “The virus may be doing things that are not under our magnifying glass and we can’t actually see,” he said. 
Itmay have given up some of its ability to cause harm when it became more transmissible, Luban said.
Eventually, a variant will become so dominant that none other will be able to outcompete it and the pace of change will slow down, Karim said. Some experts thought delta had reached that point. He thinks there are several variants left to come.
Until then, and to combat the lingering uncertainties of omicron, everyone should be getting vaccinated and boosted, wearing masks, opening windows and avoiding crowds, he and others said.
“We’ve learned the same lesson again and again,” Luban said. “The virus is transmitted in enclosed spaces with lots of people congregating. And masks work.”
Contact Karen Weintraub at
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.


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