Omicron cases are less likely to require hospital treatment, studies show

A lower percentage of people infected Coronavirus variant Omicron According to healthcare data from South Africa, Denmark and the UK, there is a greater likelihood of requiring hospital treatment compared with cases of the Delta strain.

The findings by separate research groups raise hopes that there will be fewer cases of serious illness than those caused by other strains of the virus, but the researchers warn that the extent of transmission High contamination of Omicrons can still strain health services.

The reduction in severe illness may stem from Omicron’s larger tendency, compared with other variants, to infect people who have been vaccinated or previously infected, the experts stress, the experts stressed. , although studies in the UK also suggest a potential reduction in intrinsic severity.

Unvaccinated groups are still at greatest risk, but because the majority of Omicron breakouts and re-infections are mild, the percentage of all cases developing severe disease is lower compared with variants is different. This strain now accounts for the majority of Covid-19 cases in several countries, including America.

An analysis of English-language data by researchers at Imperial University found that Omicrons were less likely to develop severe disease in any individual after adjusting for factors including age, sex, and status. Less than 11% of baseline health status, immunization status and previous infections.

At the population level, this reduces the risk of hospitalization by 25% compared to Delta, with a sharper reduction due to the fact that Omicron cases are more likely than Delta cases in already infected individuals. disease or previous vaccination, providing significant protection against serious illness.

Research in South Africa, conducted by the country’s National Institute of Infectious Diseases, found that among people who tested positive in October and November, cases were suspected of Omicron. 80% less likely to be hospitalized than hospitalized Delta cases, after adjusting for factors including prior infection. But the researchers stress that they did not take into account vaccination status in this analysis and that data on previous infections is unreliable.

A second analysis from the same research group, this time controlling for vaccination status, found that once hospitalized, the Omicron and Delta cases from recent weeks both had the potential to progress to a more serious condition. equally serious. The analyzes included more than 10,000 Omicron cases and more than 200 hospital admissions.

Graph showing research from South Africa showing Omicron cases less likely to require hospitalization than other variants

“Something is happening. . . Professor Cheryl Cohen, an epidemiologist at the University of the Witwatersrand and one of the study’s authors, said of the difference in immune responses to Omicron and Delta.

These findings suggest that breakthrough and reinfection infections from Omicron are “less severe,” she said, and that immune defense against T cells and B cells “mediates” this ” progression to severe disease” of Omicron despite reduced antibody protection.

Cohen said reducing the burden on hospitals has allowed South Africa to handle the Omicron wave without imposing containment measures but she warned that the findings may not apply to other countries. The West has an older population.

“It’s about what [Omicron] which means in absolute terms, if the number is that large, it can still cause a significant public health problem even if the risk of severe illness is less in each case,” she added. .

In addition, the Danish data show that among those who tested positive between November 22 and December 15, Omicron cases were three times less likely to be hospitalized than cases with other variations. But experts warn that Omicron outbreak concentrations in younger groups could skew the data.

The graph shows that so far, Omicron cases in Denmark are younger than cases from other variants

Henrik Ullum, director of Statens Serum Institut, Denmark’s public health agency, said: “It’s mostly young and vaccinated people who are infected with Omicron, and as we regulate this, they I see no evidence that Omicron will lead to milder disease” at a news conference on Wednesday.

But while there is limited evidence of any reduction in intrinsic severity, this does not rule out Omicrons leading to less severe outcomes at the population level, due to higher case rates in People are protected against serious illness through prior infection or vaccination.

“Due to Omicron’s higher immune evasion, this model [of fewer cases being hospitalised] Professor Samir Bhatt, professor of machine learning and public health at the University of Copenhagen and a member of the UK government’s SPI-M modeling team, will continue the assessment at the population level.

The graph shows a much lower proportion of Omicron cases in unvaccinated Denmark compared with cases from other variants

UK government awaits new data on severity of Omicron before deciding on further restrictions in the UK. But Bhatt said the UK’s approach was “Panglossian”, adding that it “exaggerated the hope offered by reducing the severity”.

Professor Thea Kolsen Fischer, head of virology and microbiology specialist diagnostics at Statens Serum Institut, said: “I feel that the increase in hospital pressure will be slower and less frequent because the vaccine seems to still be. have a protective effect.

But she added that policymakers should be “a little careful in making the narrative that it’s softer” because it will be “several weeks” before the variation’s impact on hospitals. become clear.

“I fear it because of Omicron’s ability to infect. . . what we see right now will be very different in just about two weeks,” she said.

On Sunday, Denmark introduced a series of measures to prevent The spread of Omicron, including the closure of theaters and museums as well as capacity limits at bars, restaurants and shopping malls.

Professor Peter Garred, a clinical immunologist at Copenhagen’s Rigshospitalet Largest Hospital, said the drop in severity could prompt countries, such as the UK and US, to decide not to impose the restrictions. limited “only in terms of therapeutic potential”.

“The question of whether Omicron is lightweight hasn’t really entered the discussion about the new restrictions [in Denmark],” said Garred. “The government is anticipating problems because the infection rate is going up so badly, no matter how severe.”

Cohen of the University of the Witwatersrand said Omicron waves could “spread out differently” in the Northern Hemisphere as it coincides with winter but she added that positive signs from South Africa have “a lot of relevance to countries”. other and how they react”.

“Most populations have had previous infections or vaccinations, or both,” says Cohen. “If it holds up, it’s likely that all countries will see the same impact on us.”

https://www.ft.com/content/19065fba-025c-43fd-bd76-37234af97953 Omicron cases are less likely to require hospital treatment, studies show

Huynh Nguyen

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