Omicron is less severe than previous variants of Covid because it doesn’t cause as much damage to the lungs, a series of studies have suggested.
A study by a consortium of American and Japanese scientists on hamsters and mice found that people infected with Omicron had less lung damage, lost less weight, and were less likely to die than those with other variants.
He found that mice infected with Omicron had a tenth less virus in their lungs compared to those with other variants.
The results corroborate another article written by researchers at the University of Hong Kong, who studied human tissue from Omicron victims.
They found that Omicron grew significantly slower in 12 lung samples than earlier strains of the virus.
Experts believe that the fact that the super mutant variant tends not to replicate as much in the lower parts of the lungs means that it causes less damage, which could be the cause of its reduced severity.
Data from South Africa has shown that people with Omicron are up to 80% less likely to end up in hospital than those with Delta. And a similar study by UK Health and Security estimated the risk to be 70% lower.
Roland Eils, a computer biologist at the Berlin Institute of Health, said that there is an emerging theme in the literature suggesting that the variant tends to stay outside the lungs.
A study by a consortium of American and Japanese scientists on Syrian mice found that people infected with Omicron (right) had less lung damage, lost less weight, and were less likely to die than those with the Delta variant (to the left)
The results corroborate another article by researchers at the University of Hong Kong, who studied human tissue from Omicron victims (purple bars). They found that Omicron grew significantly slower in 12 lung samples than earlier strains of the virus.
Their study, which was not peer reviewed and was published on the preprinted website medRxiv, found that of the 10,547 Omicron cases identified between October 1 and November 30, 261 (2.5 %) were admitted to hospital. For comparison, among the 948 non-Omicron cases during the same period – almost all of which would have been Delta, which was responsible for 95% of cases before the emergence of Omicron – 121 people have been hospitalized (12.8%). Researchers said those who caught Omicron had an 80% lower risk of requiring hospital care.
Omicron is milder, another study finds
People who catch Omicron are 80% less likely to be hospitalized than those who catch Delta, suggests a major study from South Africa.
Real-world analysis, of more than 160,000 people, showed that people with Omicron were also 70% less likely to be admitted to intensive care or put on a ventilator than those with Delta.
South African doctors have been insisting for weeks that Omicron has been gentler since sounding the alarm on November 24 and accused the UK of panicking over Omicron.
But researchers from the National Institute of Communicable Diseases (NICD) who conducted the study, which has yet to be peer reviewed, said it still does not respond if Omicron is inherently weaker than Delta. .
“It is difficult to disentangle the relative contribution of high levels of prior population immunity versus lower intrinsic virulence at lower disease severity observed,” the researchers concluded.
It is believed that the immunity built up from three previous waves of the virus and vaccines do the heavy lifting to keep patients out of the hospital this time around.
Up to 70% of South Africans are believed to have had Covid in the past and only around a quarter are doubly vaccinated, with boosters not yet widely available.
He told the New York Times: “It’s fair to say that the idea of a disease that manifests primarily in the upper respiratory system is emerging. “
The first article, which was published as a pre-print on Search gate and has not yet been peer reviewed, examined tissue samples in mice and hamsters.
The researchers evaluated different parts of the lungs of mice infected with the Omicron variant as well as other strains of the virus, including Delta.
They found that people infected with Omicron had much less severe symptoms.
And they were particularly struck by how Syrian hamsters – a breed particularly susceptible to previous strains – exhibited lower disease levels with the variant.
Dr Michael Diamond, a virologist at the University of Washington and co-author of the study, said: “It was surprising, because all of the other variants heavily infected these hamsters.”
Meanwhile, the second study by scientists in Hong Kong – also not peer reviewed – looked at Omicron in human lung cells.
They found that the virus replicates much less in the lower parts of the lungs.
The researchers also studied cells in the bronchi – the tubes in the upper part of the chest that carry air to the lungs – and found that the variant was 70 times more noticeable in these cells.
They said the prevalence of the virus in the upper parts of the chest makes it more transmissible because it is expelled faster by the breath.
But they said its lower levels in the lungs could also be the cause of the reduced severity suggested by many other studies.
They wrote: “These observations may suggest that Omicron may have reduced clinical severity, but such interpretations need to be qualified as the severity of Covid-19 disease is determined not only by virus replication but also by responses. deregulated innate immune systems. ”
It comes after a UK analysis of more than one million Omicron and Delta cases over the past few weeks found the risk of hospitalization with the now-dominant variant is around one-third that of his predecessor.
Britain is seeing an increase in Covid cases due to the highly transmissible variant, with record daily infections of 189,846 yesterday.
As hospital admissions started to increase, the government said it believed the new variant was milder than the Delta variant.
The number of patients requiring mechanical ventilation beds also remained stable through December, unlike previous peaks in the pandemic.
The analysis was released by the UK Health Safety Agency, after working with the MRC Biostatistics Unit at Cambridge University to analyze 528,176 Omicron cases and 573,012 Delta cases.
He also found that vaccines can work well against Omicron.
“In this analysis, the risk of hospitalization is lower for Omicron cases presenting with symptomatic or asymptomatic infection after two and three doses of the vaccine, with an 81% reduction (…) in the risk of hospitalization after three doses compared to unvaccinated Omicron cases, “the UKHSA said.
Susan Hopkins, chief medical adviser at the UKHSA, said the scan was in line with other encouraging signs on Omicron, but said the health department could still struggle with such high transmission rates.
“It is still too early to draw definitive conclusions about the seriousness of the hospitals, and the increased transmissibility of Omicron and the increase in cases in the over-60 population in England means that it remains very likely that it there will be significant pressure on the NHS in the coming weeks “she said.