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* 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
(Recasts, adding expert comment)
By Guy Faulconbridge and Alistair Smout
LONDON, Feb 4 (Reuters) - British researchers are to explore
mixing doses of the Pfizer and AstraZeneca
COVID-19 vaccines in a world first trial aimed at finding new
ways to swiftly reduce coronavirus infections as new mutated
variants emerge.
While thousands of individual changes have arisen as the
virus mutates on replication and evolves into new variants, only
a tiny minority are likely to be important or change the virus
in an appreciable way, according to the British Medical Journal.
Among coronavirus variants currently most concerning for
scientists and public health experts are the so-called British,
South African and Brazilian variants, which appear to spread
more swiftly than others.
British Vaccine Deployment Minister Nadhim Zahawi said
current COVID-19 vaccines would probably still protect people
against infection with the new variants, but this would need to
be closely monitored.
"Its very unlikely that the current vaccine won't be
effective on the 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."
Ravi Gupta, a professor of microbiology at Cambridge
University, said Zahawi had misspoken and was referring to
individual mutations, not variants.
"The number of mutations has little actual relevance as many
mutations emerge and disappear continuously," Gupta said.
"Scientists are using ‘variants’ to describe viruses with
mutations that are transmitting in the general population –
there aren’t 4,000 of those."
The so-called British variant, known as VUI-202012/01 or
B.1.1.7., has mutations including a change in the spike protein
that the coronavirus uses to bind to the human ACE2 receptor -
meaning that it is probably easier to catch.
"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 COVID-19 pandemic has killed 2.268 million people
worldwide since it emerged in China in late 2019, according to a
Reuters tally.
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 responses to 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 vaccine could
help understanding of whether shots can be rolled out with
greater flexibility, and might even increase immunity.
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)
