GENEVA, Dec. 13 (Reuters) – The Omicron variant of the coronavirus, reported in more than 60 countries, poses a “very high” global risk, with some evidence that it eludes vaccine protection, but clinical data on its severity are limited, according to the World Health Organization says.

Considerable uncertainty surrounds Omicron, first detected last month in southern Africa and Hong Kong, whose mutations could lead to higher transmissibility and more cases of COVID-19 disease, WHO said in a technical note published Sunday.

“The overall risk with the new variant of concern Omicron remains very high for a number of reasons,” he said, reiterating his first assessment of November 29.

At least one patient has died in the UK after contracting the Omicron variant, UK Prime Minister Boris Johnson said on Monday.

The WHO said there were early signs that those vaccinated and previously infected would not produce enough antibodies to ward off an infection from Omicron, leading to high transmission rates and “serious consequences.”

It is not clear whether Omicron is inherently more contagious than the globally dominant Delta variant, the WHO said.

Corroborating the WHO assessment, researchers at the University of Oxford released a lab test on Monday that recorded a substantial drop in neutralizing antibodies against Omicron in people who had received two doses of the COVID-19 vaccine. Read more

While the antibody defenses of the AstraZeneca (AZN.L) and BioNTech / Pfizer vaccines have been weakened, there is hope that T cells, the second pillar of an immune response, may prevent serious disease by attacking the cells. infected human cells.

PROTECTION THRESHOLD?

A number of those vaccinated did not produce measurable neutralizing antibodies against Omicron, the Oxford researchers said. One of them, Matthew Snape, said it was not yet clear how pronounced the actual decline in vaccine effectiveness would be.

“We don’t know how many neutralizing antibodies are enough. We still haven’t really determined what the level of protection is,” Snape said, adding that the best advice for people not yet vaccinated is to seek initial treatment and for vaccinated people to receive boosters.

Oxford researchers said there was no evidence Omicron caused more serious illness.

Their results were broadly in line with another lab test last week on the blood of twice vaccinated individuals conducted by researchers at the Medical University of Innsbruck, Austria.

The analysis also recorded a significant drop in antibodies reacting to Omicron, with many blood samples showing no response.

The Innsbruck and Oxford teams said they would expand their search to those who have received three vaccines.

Pfizer and BioNTech said last week that two injections of their vaccine could still protect against serious illness, as its mutations were unlikely to escape T-cell response. Read More

They also said that a third booster restored a level of antibody protection against Omicron comparable to that conferred by a two-shot regimen against the original virus identified in China.

WHO has cited preliminary evidence that the number of people re-infected with the virus has increased in South Africa.

While early results suggest Omicron may be less severe than the Delta variant, more data is needed to determine whether Omicron is inherently less dangerous, he said.

“Even though the severity is potentially less than that of the Delta variant, hospitalizations are expected to increase due to increased transmission. More hospitalizations can strain health systems and lead to more death, “he said.

More information was expected in the coming weeks, he added, noting the lag between infections and results.

Reporting by Stephanie Nebehay in Geneva, Ludwig Burger in Frankfurt, editing by William Maclean, Robert Birsel and Barbara Lewis

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