The Omicron SARS-CoV-2 variant has been spreading rapidly in the United States since December 2021 and appears to be much more contagious than earlier strains of the coronavirus.
With infections at all-time highs in the U.S., some news outlets are starting to suggest that the latest form of coronavirus carries a lower chance of getting seriously ill, but experts at the World Health Organization (WHO) and leading epidemiologists have said the Omicron variant is anything but mild for most people.
Scientists at Case Western Reserve University have presented preliminary evidence that the risk of being admitted to the hospital or the intensive care unit during the omicron surge in the U.S. is about half of the risk observed during the delta surge.
This reflects what doctors across the country are now seeing firsthand with their patients, but data on the severity of the disease caused by the Omicron variant compared with the Delta variant is limited.
“While Omicron does appear to be less severe compared to Delta, especially in those vaccinated, it does not mean it should be categorized as mild,” WHO Director-General Tedros Adhanom Ghebreyesus told reporters in Geneva on Thursday.
“Just like previous variants, Omicron is hospitalizing people and it is killing people … In fact, the tsunami of cases is so huge and quick, that it is overwhelming health systems around the world,” said Tedros.
Leading epidemiologists agree.
“There are two reasons WHO are being cautious about this,” said Professor Adrian Esterman, an epidemiologist from the University of South Australia. “The first is that, even if it’s milder, there are so many people now being infected that even a small proportion of them getting severely ill is a lot of people.”
“And the second reason is, we simply don’t have the data to say that it is milder in many countries that have got a high proportion of unvaccinated people,” Esterman said.
The tsunami of Omicron cases is coming on so quickly and so broadly, that it is overwhelming health systems around the world.
Early research has suggested that the Omicron variant causes COVID-19 symptoms among the fully vaccinated, but there have been more cases among the fully vaccinated than with Victoria, Beta and Delta variants.
A new study from researchers at the University of Oxford found that two doses of the Oxford-AstraZeneca or Pfizer-BioNTech vaccine were less effective at stopping the omicron variant compared to previous variants.
These increased breakthrough infections in previously infected or double vaccinated individuals could drive a further wave of infection that drives up hospital admissions and overwhelms health care capacity.
Gavin Screaton, head of Oxford University’s Medical Sciences Division, said that studies show evidence that booster shots are needed.
“Whilst there is no evidence for increased risk of severe disease, or death, from the virus amongst vaccinated populations, we must remain cautious, as greater case numbers will still place a considerable burden on health care systems,” said Screaton.
Screaton said that the findings should “press home the message that those who are offered booster vaccination should take it.”
“Part of the reason why it seems milder isn’t because it’s necessarily mild, but because it’s infecting people who have had vaccines,” said Nancy Baxter, head of the School of Population and Global Health at the University of Melbourne, in Australia. “It’s actually getting around our protection better than some of the other variants. So, in some ways, it’s expanding who it can infect, which isn’t really mild.”
About half a dozen recent studies from research facilities such as the Neyts Lab at Leuven University in Belgium and the University of Hong Kong suggest Omicron does not damage lungs as much as the Delta and other previous variants but those research reports have not yet been peer-reviewed by other scientists.
“Most of these studies have been done in vaccinated populations, so we simply don’t have enough data to be able to say categorically that it’s milder in the unvaccinated,” Esterman said.
There are two points those who downplay the latest variant simply are not recognizing. The first is that even with Omicron some people get severely ill and die, while the second issue is the impact on people who get infected and wind up with long-term health problems.
“So to make out this is just nothing worse than the flu is extremely poor messaging,” Esterman said.
People who get COVID-19 infections caused by the Omicron variant are not less likely to need hospital care, compared with those infected by the Delta variant, but those who have been vaccinated are more likely to suffer less severe symptoms from the disease.
Meanwhile, people who were re-infected—meaning they caught Omicron after recovering from a previous COVID-19 infection—had a lower risk of needing hospital care, likely reflecting the benefits of having some prior immunity against the same family of viruses.
“Given the high transmissibility of the Omicron virus, there remains the potential for health services to face (overwhelming) demand if Omicron cases continue to grow at the rate that has been seen in recent weeks,” said Neil Ferguson, PhD, who studies how infectious diseases spread at Imperial College London.