Health and Science

No evidence that Covid omicron variant is less severe than delta, UK study says

Key Points
  • The study used the data from the U.K. Health Security Agency and the U.K. health service for all PCR-confirmed Covid cases in England between Nov. 29 and Dec. 11.
  • The study estimates that the risk of reinfection with the omicron variant is 5.4 times greater than that of the delta variant.
  • The researchers said "hospitalisation data remains very limited at this time."
  • The study is yet to be peer-reviewed.
An employee at a testing station in the city centre takes a swab from a woman. In Lower Saxony, stricter Corona rules apply in many areas.
Hauke-Christian Dittrich | picture alliance | Getty Images

LONDON — There is currently no evidence that the new Covid-19 omicron variant is any less severe than the delta variant, according to the early findings of a study by the U.K.'s Imperial College London.

"The study finds no evidence of Omicron having lower severity than Delta, judged by either the proportion of people testing positive who report symptoms, or by the proportion of cases seeking hospital care after infection," a research team led by professor Neil Ferguson said Friday in a blog post accompanying the study.

The study used the data from the U.K. Health Security Agency and the U.K.'s health service for all PCR-confirmed Covid cases in England between Nov. 29 and Dec. 11.

However, the data included only 24 hospitalizations of patients suspected of having the omicron variant, with researchers saying "hospitalisation data remains very limited at this time." The study is yet to be peer-reviewed.

The study estimates that the risk of reinfection with the omicron variant is 5.4 times greater than that of the delta variant.

VIDEO4:5604:56
Dr. Scott Gottlieb says time is running out to get a Covid booster as omicron looms

The data implies that protection against omicron reinfection afforded by previous infection may be as low as 19%, it said. After two doses of a vaccine that protection stands between 0% and 20%, it added, with a booster jab increasing that level to between 55% and 80%.

Ferguson, a medical advisor to the British government, added in the blog post: "This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination. This level of immune evasion means that Omicron poses a major, imminent threat to public health."

The U.K. reported 93,045 cases in a single day on Friday, another record. Long queues have been seen outside vaccination centers in many U.K. cities and towns, with the government putting its booster program in overdrive to try to get a third vaccine shot to as many people as possible.

While the number of deaths remains low currently and initial reports suggest that the omicron variant might not be any more severe than other Covid strains, health experts have repeatedly warned that the sheer number of infections could lead to mounting fatalities and an overwhelmed health-care system.

The South African doctor who first spotted the variant among her patients has said that the initial symptoms she saw in her own clinic were "extremely mild" but this was observational evidence from a small group of people.

A study published this week by researchers at the University of Hong Kong's Faculty of Medicine said that the omicron variant replicates 70 times faster in human airways than delta, but infection in the lungs appears to be less severe compared with the original virus strain.

— CNBC's Holly Ellyatt contributed to this article.