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* World faces around 4,000 variants of novel coronavirus
* UK trials combining Pfizer and AstraZeneca vaccines
* UK says vaccines likely to work on different variants
* All drugmakers looking to improve vaccines for new
variants
(Adds quotes from researcher, background on trial)
By Guy Faulconbridge and Alistair Smout
LONDON, Feb 4 (Reuters) - The world faces around 4,000
variants of the virus that causes COVID-19, prompting a race to
improve vaccines, Britain said on Thursday, as researchers began
to explore mixing doses of the Pfizer and AstraZeneca
shots in a world first.
Thousands of variants have been documented as the virus
mutates, including the so-called British, South African and
Brazilian variants which appear to spread more swiftly than
others.
British Vaccine Deployment Minister Nadhim Zahawi said it
was very unlikely that the current vaccines would not work
against the new variants.
"Its very unlikely that the current vaccine won't be
effective on the variants whether in Kent or other variants
especially when it comes to severe illness and hospitalisation,"
Zahawi told Sky News.
"All manufacturers, Pfizer-BioNTech, Moderna,
Oxford-AstraZeneca and others, are looking at how they can
improve their vaccine to make sure that we are ready for any
variant - there are about 4,000 variants around the world of
COVID now."
While thousands of variants have arisen as the virus mutates
on replication, only a very small minority are likely to be
important and to change the virus in an appreciable way,
according to the British Medical Journal.
The so called British variant, known as VUI-202012/01, has
mutations including a change in the spike protein that viruses
use to bind to the human ACE2 receptor - meaning that it is
probably easier to catch.
"We have the largest genome sequencing industry - we have
about 50% of the world's genome sequencing industry - and we are
keeping a library of all the variants so that we are ready to
respond - whether in the autumn or beyond - to any challenge
that the virus may present and produce the next vaccine," Zahawi
said.
VACCINE RACE
The novel coronavirus - known as SARS-CoV-2 - has killed
2.268 million people worldwide since it emerged in China in late
2019, according to Johns Hopkins University of Medicine.
Israel is currently far ahead of the rest of the world on
vaccinations per head of population, followed by the United Arab
Emirates, the United Kingdom, Bahrain, the United States and
then Spain, Italy and Germany.
Britain on Thursday launched a trial to assess the immune
responses generated if doses of the vaccines from Pfizer and
AstraZeneca are combined in a two-shot schedule. Initial data on
immune responses is expected to be generated around June.
The trial will examine the immune responses of an initial
dose of Pfizer vaccine followed by a booster of AstraZeneca's,
as well as vice versa, with intervals of four and 12 weeks.
The trial will be the first of its kind to combine a mRNA
shot - the one developed by Pfizer and BioNtech - and a
adenovirus viral vector vaccine of the type developed by Oxford
University and AstraZeneca. AstraZeneca's shot is separately
being trialled in combination with another viral vector vaccine,
Russia's Sputnik V.
The British researchers behind the trial said data on
vaccinating people with the two different types of vaccines
could help understanding of whether shots can be rolled out with
greater flexibility around the world, and might even increase
immune responses.
Matthew Snape, an Oxford vaccinologist who is leading the
trial, said mixing different shots had proven effective in Ebola
vaccine schedules, and though the new trial mixed vaccine
technologies, it could also work.
"Ultimately, it all comes down to the same target - cells
making the spike protein - just using different platforms," he
told reporters.
"For that reason we do anticipate that we'll generate a good
immune response with these combinations."
Public Health England's head of immunisation Mary Ramsay
said there was a lot of precedent for such work, as vaccines
against Hepatitis A and B were interchangeable from two
different manufacturers, and similar work has been undertaken
for human papillomavirus (HPV).
(Reporting by Guy Faulconbridge, Andy Bruce and Alistair Smout,
editing by Estelle Shirbon and Nick Macfie)
