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By John Miller
ZURICH, Dec 30 (Reuters) - Britain on Wednesday became the
first country to approve AstraZeneca and Oxford
University's home-grown UK COVID-19 vaccine, adding an
easy-to-manage shot to the arsenal of a nation desperate for
pandemic relief.
Even so, scientists - and regulators in Europe, following
the Brexit divorce - are sceptical, given confusion over trial
results earlier that left experts questioning the robustness of
the data.
HOW DOES THE ASTRAZENECA SHOT'S EFFICACY STACK UP TO
OTHERS'?
The AstraZeneca/Oxford vaccine's overall efficacy in
preventing symptomatic infections was 70.4%, compared with the
95% efficacy of the shot from Pfizer/BioNTech, the other vaccine
approved in Britain.
Single-dose efficacy was pegged at 52.7%, Britain said on
Wednesday, in guidance to health workers, though a UK medical
adviser also said that one AstraZeneca dose should be 70%
effective after three weeks.
The UK regulator recommends a booster shot four to 12 weeks
after the first dose, because up to 80% efficacy was reached
with a three-month interval between shots, an official involved
in the approval decision by the Medicines and Healthcare
products Regulatory Agency (MHRA) said.
Confusion over efficacy emerged after interim late-stage
trial results announced in late November when AstraZeneca
acknowledged that people in its clinical trial accidentally got
different doses.
Those who received a half dose of the vaccine, followed by a
full dose, were shown to have 90% protection, the company said
initially, while two full doses offered only 62% protection.
Now, however, the MHRA said the half-dose regimen's results
were not borne out in analysis.
"It's all much more confusing because mistakes have been
made, genuinely," one European Medicines Agency (EMA) official
told Reuters. "Mistakes that resulted in clinical data that was
much more complex to interpret than Moderna's and Pfizer's. And
on top of that the efficacy is lower."
WHAT ARE THE OTHER DIFFERENCES?
Technology, price and storage.
The AstraZeneca shot is a "viral vector vaccine", where a
specially engineered virus that normally causes chimpanzees to
get the common cold delivers genetic instructions to human cells
to make the spike protein jutting out from the new coronavirus's
surface.
The Pfizer/BioNTech and Moderna vaccines use a new
technology which packs messenger RNA (mRNA) inside tiny fat
droplets to instruct cells to make the spike protein.
AstraZeneca pledged the vaccine would cost just a few
dollars per dose and be sold without making a profit, whereas
Pfizer's vaccine costs $18.40-$19.50 per dose.
A separate mRNA vaccine from Moderna, approved in the United
States, costs up to $37.
The AstraZeneca shot doesn't require deep freezing at minus
70 degrees like the mRNA vaccine from Pfizer and its
German partner, BioNTech , and has already
been produced by the millions of doses.
It can be kept in a standard refrigerator for six months.
It's also cheaper to make, bringing hope to developing
countries largely left out of the early vaccine haul.
NOW THAT THE UK HAS APPROVED THE VACCINE, WILL OTHER
GOVERNMENTS FOLLOW?
When Britain signed off on Pfizer/BioNTech's vaccine in
early December, that pressured regulators elsewhere, and the
United States and Europe followed in short order.
Moderna's similar mRNA vaccine has also received
U.S. approval.
Britain's move now to back AstraZeneca's shot prioritises
getting as many people inoculated quickly, before all the
answers about efficacy and optimal dosing are in.
Absent safety concerns, British regulators may be making a
trade-off between waiting for perfection and making do with what
they have.
"A swift emergency approval implies taking the risks of a
lower (or) shorter efficacy than may be reached with mRNA
vaccines," said Claire-Anne Siegrist, vaccinology and immunology
head at Geneva's University Hospitals.
While an EMA official said this week the shot is unlikely to
be approved before the end of January, a top German vaccine
official said on Wednesday he still expected a "quick decision"
by Europe since its rolling review process is well advanced.
The EU drug watchdog is carrying out a review for a
conditional market approval, rather than the UK's speedier
emergency use approval.
India's drug regulator is also discussing emergency approval
of the AstraZeneca vaccine, being made in partnership with the
Serum Institute of India.
WHO WILL GET WHICH VACCINE?
England's National Health Service will not give people a
choice of vaccine.
But with several now available, countries need to decide who
should get which vaccine, as some people may prefer the shots
with higher efficacy.
Experts said the differences between the efficacy rates are
significant, prompting tough choices.
"In countries where both the mRNA and the AstraZeneca
vaccines would be available, whom do you decide to give the less
effective vaccine?" Siegrist said.
Thomas Mertens, head of STIKO, Germany's expert panel on
vaccine use, told Reuters that his group plans to address this
issue "in the near future" as it hopes to tailor a strategy that
makes the biggest impact with limited supplies.
Some experts, however, said that choice may be a luxury
countries cannot afford.
"At this juncture, we don't have vaccine in sufficient
quantities to reach all those who need it," said Thomas
Klimkait, a University of Basel professor and researcher who is
working on a Swiss SARS-CoV-2 vaccine project.
"I would say at this moment that every vaccine with
relatively good efficacy - that means, at least 60 or 70% -
should be put to use, when it has an appropriate safety
profile."
(Reporting by John Miller in Zurich, Stephanie Nebehay in
Geneva, Emilio Parodi in Milan, and Deena Beasley in New York;
Editing by Josephine Mason and Giles Elgood)
