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home / 世界杯决赛2022

is omicron really milder than other covid-19 variants? it's complicated

omicron is better at slipping around vaccine-induced immunity, but vaccines are still effective against severe disease, meaning the shots are blunting its impact

by sharon kirkey

feb 11 2022
read time 3 minute read
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is omicron truly milder than delta? is there something intrinsically different about the variant? or, has it just bumped up against a lot of people with immunity from vaccination and old infections?

“there is support for both scenarios,” south africa-based virologist alex sigal writes in a commentary in nature reviews immunology.

lab studies suggests that, compared to other variants, omicron gets into human cells differently, that it’s restricted mostly to the upper respiratory tract and less likely to lodge and spread in the lungs, where it causes more severe disease, sigal wrote.

“it’s replicating in places that cause less damage,” infectious disease expert sumit chanda told the scientist magazine.

studies in humans have also found significantly reduced odds of severe disease and death for the omicron-infected compared to the delta-infected.

imperial college london researchers were the first to report in december that omicron appeared less likely to put people in hospital, or keep them there for more than a day, compared to those with delta.

more studies and reports since, from south africa, southern california and the u.s. centers for disease control and prevention have found that people with confirmed omicron are substantially less likely to be admitted to hospital, require oxygen therapy or mechanical ventilation or die, compared with confirmed delta cases.

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“despite omicron seeing the highest reported numbers of covid-19 cases and hospitalizations during the pandemic, disease severity indicators, including length of stay, icu admission, and death, were lower than during previous pandemic peaks,” the cdc reported.

in south africa, where the variant was first identified, omicron entered a population “that had considerably more immunity than any previous sars-cov-2 variant had encountered,” harvard university epidemiologist william hanage and infectious diseases physician roby bhattacharyya write in the new england journal of medicine .

and while omicron is better at slipping around vaccine-induced immunity, causing breakthrough infections, “vaccines’ effectiveness against hospitalization is largely preserved,” meaning the shots are blunting omicron’s impact.
the unvaccinated have a five-fold higher chance of being hospitalized because of omicron compared to those doubly vaccinated with pfizer.

“there must be a renewed push to vaccinate and boost those not yet protected, because omicron is not necessarily intrinsically milder,” hanage said in a release.

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things would have been “much, much worse” with delta, hanage, co-director of the center for communicable disease dynamics at the harvard t. h. chan school of public health wrote in time magazine . but even “mild” omicron has caused more than 2,400 deaths in the u.s. per day, on average, in the past week.

“i think there’s genuine good news about both intrinsic severity appearing to be slightly lower and immunity holding decently well against severe disease, far better than it is against infection,” bhattacharyya told the scientist. “i just find myself a bit concerned about the oversimplified narrative that ‘omicron is milder,’ or even worse, ‘omicron is mild.’ the nuances matter here, i think.”
more people need to get vaccinated, given that more infections give the virus more opportunities to mutate.
more people need to get vaccinated, given that more infections give the virus more opportunities to mutate. getty images
globally, millions of new infections from omicron have been recorded. the more infections, the more opportunities for the virus to mutate. “the emergence of another major variant of concern is highly probable as the virus has proven it can evolve to escape immunity in the current climate of infection,” sigal said.

“infection is the fuel that evolution has, to bring us these new variants,” mathematician and epidemiologist caroline colijn of simon fraser university said in a recent interview with national post . “we need to get infection numbers down.”

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the uncertainty is how long immunity from vaccination and exposure to omicron lasts. “those things will all affect how many new infections are happening per day, or per week, after this peak,” colijn said.

“the silver lining — this is not a positive, but we will have really good immunity, and a lot of people unfortunately will have had omicron. but hopefully that will also mean a lot of people who are recovered and who are not vulnerable to infection again over the coming months.

“hopefully we’re going to enter into a phase of low levels of virus … and able to move into an era where it’s low for some extended time, and if it rises again doesn’t cause severe disease,” she said.
“i think we should hope for the best, but not necessarily plan for nothing but the best.”

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sharon kirkey
sharon kirkey
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