New UK study strengthens conclusion Omicron causes less severe disease


LONDON — People infected with the Omicron variant of the coronavirus are between 50 and 70% less likely to be admitted to hospital than those who have caught previous strains, new UK study adds to growing number evidence of reduced severity of Omicron in populations with high level of immunity.

The scan from England, released by the UK’s Health Security Agency on Thursday, follows studies in Scotland and South Africa that also found a significantly lower risk of hospitalization with Omicron than ‘with more established variants, including Delta.

Scientists still don’t know how these encouraging hospitalization results will compare to Omicron’s much higher transmissibility and ability to partially evade vaccine protection. The risk, they say, is that the variant could still cause a big wave of hospital admissions just by infecting many more people.

The Health Security Agency said that in a analysis of around 500,000 cases of Covid-19 he found that the risk of hospitalization with Omicron was between 50% and 70% lower with Omicron than with Delta, and that the risk of being admitted, or of going to an emergency department without being admitted, was about 40% lower.

The agency warned that its findings are preliminary and based on a small number of hospitalized cases. He also said he might underestimate the risk of admission as few cases have yet been detected in the older and more vulnerable age groups.

In a less encouraging conclusion, the agency said the effectiveness of a booster dose in preventing mild symptoms of Omicron appears to wane over time, although it said the boosters should still protect against disease. serious.

The agency said that after 10 weeks, the effectiveness of the vaccine against the symptomatic disease after a third dose of the vaccine developed by Pfizer Inc.

and BioNTech SE in Germany fell to 45%, from 70% previously, among those who received Pfizer as the main treatment in two doses.

In those who received a Pfizer booster after two doses of AstraZeneca‘s

vaccine, the efficacy after 10 weeks increased from 60% to 35%. The vaccine developed by Moderna Inc.

held up better as a booster among those who received either Pfizer or AstraZeneca for their primary course.

The findings, however, add to a series of encouraging data on Omicron’s severity from other real-world research.

A University of Edinburgh study released on Wednesday, drawing on the health records of 5.4 million people in Scotland, found that the risk of hospitalization with Covid-19 was two-thirds lower with Omicron than ‘with Delta.

A hospital in London. Nearly 120,000 positive tests for the Covid-19 virus were reported in the UK on Thursday


justin tallis / Agence France-Presse / Getty Images

A separate study, also released Wednesday, by researchers at the South African National Institute of Communicable Diseases also found that people infected with Omicron were 70 to 80 percent less likely to need hospital treatment than people infected with previous variants, including Delta.

Scientists warn that the reduction in severity seen in these studies is mainly due to immunity, either high levels of vaccination, in the case of England and Scotland, or high levels of previous exposure to the virus, as in South Africa.

Much less is known about Omicron’s inherent severity and whether it is a milder strain of coronavirus than those that came before it. A separate analysis of recent Covid-19 cases in England by Imperial College London, released on Wednesday, suggested that the risk of hospitalization with Omicron is only around 10% to 11% lower than that of Delta for a person who has not been vaccinated and has never been infected before, demonstrating the protection that persists against the new variant resulting from vaccination or exposure to the virus.

Omicron is quickly overtaking Delta as the dominant strain of the virus in much of the world, including the United States, where the Centers for Disease Control and Prevention estimates it accounts for about three-quarters of recent cases, although it was only detected for the first time by scientists. in South Africa in November.

In the UK, the variant is already dominant and is fueling a big wave of infection. Nearly 120,000 positive tests for the virus were reported Thursday, a new daily record. Hospital admissions are increasing, but at around 900 per day, they are well below the 4,000 per day seen during the deadliest phase of the pandemic in January.

Write to Jason Douglas at [email protected]

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