The omicron variant can affect the lungs differently, studies say

Recent studies suggest that the omicron variant of coronavirus may be less severe than delta because it affects the lungs in different ways.

In a recent White House briefing, the COVID-19 response team told White House Chief Medical Officer Dr. Anthony Fauci, to reporters, said a study from Hong Kong showed that although the variant of concern replicates faster than delta in the bronchi, there is “less efficient replication in the lung.”


“Hamster models from the University of Tokyo show that omicron poorly infects and spreads in the lungs and is less pathogenic compared to participating in a hamster model. Belgian researchers in Syrian hamsters see the same thing,” he said. “NIH-funded studies currently underway in both mice and hamsters confirm the minor virulence in the animal model. And studies here at the Vaccine Research Center at NIH, in the non-human primate model, are ongoing and will await the results of it. . “

Fauci said the data is still preliminary in many respects, but that “all indications point to a minor severity of omicron versus delta.”

“It is difficult to determine what degree of diminished severity is due to pre-existing immunity or the inherently lower virulence of omicron, as suggested by animal experiments, or a combination of both. Increased transmissibility of omicron, resulting in an extremely large number of cases , may override some of the effects of the lower disease severity, “he added. “And then we should not become complacent, as our hospital system may still be stressed in certain areas of the country.”

Dr. Anthony Fauci, Chief Medical Advisor to the White House and Director of NIAID, joins the White House COVID-19 Response Teams regular calls with the National Governors Association on Monday, December 27, 2021 in Washington, DC
(AP Photo / Carolyn Kaster)

In research that has not yet been peer-reviewed, authors from the University of Cambridge and the University of Tokyo reported that omicron could be significantly better than previous variants in avoiding vaccine-induced antibodies.

To reach these conclusions, Dr. Kei Sato, Dr. Ravi Gupta and other synthetic viruses that carried key mutations found in omicron and delta. These “pseudoviruses” were tested against blood samples from vaccinated individuals who had received two doses of either the AstraZeneca or Pfizer-BioNTech vaccines.

To understand how effective omicron is at penetrating cells, the team used the synthetic viruses to infect cells in lung organs.


The University of Cambridge explained in a publication that despite having three mutations that were predicted to favor cleavage, the omicron spike protein was found to be less effective than the delta tip in cleaving the ACE2 protein receptor – found on the surface of Cells in the lung – and into the lung cells.

Once omicron had entered the lung cells after cleaving the ACE2 receptor, it was also less able than delta to cause fusion between cells – something often seen in respiratory tissue taken after serious illness.

“Although further work is needed to confirm these findings, there are general indications that omicron mutations present the virus with a double-edged sword: it has become better at evading the immune system, but it may have lost some of its ability to cause serious illness. “said Gupta.

The World Health Organization (WHO) and top officials have warned that it is too early to be reassured by the first data suggesting that omicron leads to milder disease, and Gupta urged people to continue to be cautious.

“Omicron still represents a major public health challenge. Individuals who have received only two doses of the vaccine – or worse, none at all – are still at significant risk for COVID-19 and some will develop serious disease. The large number of new cases we see every day, reinforces the need for everyone to get their boosters as soon as possible, “he added.

In a Wednesday report, an international group said hamsters and mice infected with omicron had fewer lung injuries, did not lose as much weight and were less likely to die.

While animals infected with omicron generally experience milder symptoms, the group found that omicron levels in rodent lungs were one-tenth or less of the level of other variants.

“Although these results are consistent with the very preliminary clinical data in humans, suggesting that B.1.1.529 causes a more transmissible but possibly milder respiratory infection, the basis for the attenuation in rodents remains unknown,” the report’s researchers wrote, noting that studies are underway to determine the basis of attenuation in mice and hamsters and to find out how this is related to the patterns of omicron infection seen in humans.


Since the omicron variant was first discovered in the United States, states have seen a record number of cases and hospitals are beginning to be replenished.

New COVID-19 cases have risen to their highest level to date, averaging more than 265,000 a day, according to data from the Johns Hopkins University Coronavirus Resource Center.

Researchers have observed the pathogen in laboratories – working to learn more about its transmissibility, severity and ability to avoid vaccines and immune response while omicron continues to infect around the world.

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