Last checked at 
(Adds quotes from Oxford researchers, adds Innsbruck study)
By Stephanie Nebehay and Ludwig Burger
GENEVA, Dec 13 (Reuters) - The Omicron coronavirus variant,
reported in more than 60 countries, poses a "very high" global
risk, with some evidence that it evades vaccine protection but
clinical data on its severity is limited, the World Health
Organization says.
Considerable uncertainties surround Omicron, first detected
last month in southern Africa and Hong Kong, whose mutations may
lead to higher transmissibility and more cases of COVID-19
disease, the WHO said in a technical brief issued on Sunday.
"The overall risk related to the new variant of concern
Omicron remains very high for a number of reasons," it said,
reiterating its first assessment https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-poses-very-high-global-risk-countries-must-prepare-who-2021-11-29
of Nov. 29.
At least one patient has died in the United Kingdom after
contracting the Omicron variant, British Prime Minister Boris
Johnson said on Monday.
The WHO said there were early signs that vaccinated and
previously infected people would not build enough antibodies to
ward off an infection from Omicron, resulting in high
transmission rates and "severe consequences".
It is unclear whether Omicron is inherently more contagious
than the globally dominant Delta variant, the WHO said.
Corroborating the WHO's assessment, University of Oxford
researchers published a lab analysis on Monday that registered a
substantial fall in neutralising antibodies against Omicron in
people who had had two doses of COVID-19 vaccine.
While the antibody defences from courses of AstraZeneca
vaccine and BioNTech/Pfizer have been undermined, there
is hope that T-cells, the second pillar of an immune response,
can prevent severe disease by attacking infected human cells.
THRESHOLD OF PROTECTION?
A number of vaccine recipients did not produce any
measurable neutralising antibodies against Omicron, the Oxford
researchers said. One of them, Matthew Snape, said it was not
yet clear how pronounced the real-world decline in vaccine
efficacy will be.
"We don’t know how much neutralising antibody is enough. We
still haven’t really pinned down what is the threshold of
protection," Snape said, adding the best advice for the
not-yet-vaccinated is to seek an initial course and for those
vaccinated to get booster shots.
The Oxford researchers said there was no evidence yet
Omicron caused more severe disease.
Their findings were broadly in line with another lab
analysis https://www.medrxiv.org/content/10.1101/2021.12.08.21267491v1.full.pdf
last week on the blood of twice-vaccinated individuals
conducted by researchers at the Medical University of Innsbruck,
Austria.
The analysis also registered a significant drop in
antibodies reacting to Omicron, with many blood samples showing
no response at all.
Both the Innsbruck and the Oxford teams said they would
widen their research to those who had three vaccine shots.
Pfizer and BioNTech said last week that two shots of their
vaccine may still protect against severe disease, because its
mutations were unlikely to evade the T-cells'
response.
They also said a third booster shot restored a level of
antibody protection against Omicron comparable to that conferred
by a two-shot regimen against the original virus identified in
China.
The WHO cited preliminary evidence that the number of people
getting reinfected with the virus has increased in South Africa.
While early findings suggest that Omicron may be less severe
than the Delta variant, more data is needed to determine whether
Omicron is inherently less dangerous, it said.
"Even if the severity is potentially lower than for the
Delta variant, it is expected that hospitalisations will
increase as a result of increasing transmission. More
hospitalisations can put a burden on health systems and lead to
more deaths," it said.
Further information was expected in coming weeks, it added,
noting the time lag between infections and outcomes.
(Reporting by Stephanie Nebehay in Geneva, Ludwig Burger in
Frankfurt, Editing by William Maclean, Robert Birsel and Barbara
Lewis)
