By Jenny Strasburg
LONDON -- AstraZeneca PLC and the University of Oxford said
their Covid-19 vaccine was as much as 90% effective in preventing
infections without serious side effects in large clinical trials,
boosting hopes that a third Western-developed shot could be
authorized for use before the end of the year.
The partners said Monday that there were no confirmed serious
safety events related to the vaccine and that it was well tolerated
across different dosing regimens. Its efficacy ranged from 62% to
90% depending on the dosage given, with an average of 70%, they
The results of the early analysis bode well for the near-term
availability of a third vaccine to battle Covid-19, after a shot
created by Moderna Inc. and one made jointly by Pfizer Inc. and
Germany's BioNTech SE were found to be more than 90% effective in
their own late-stage trials. Pfizer and BioNTech last week said
they had asked the U.S. Food and Drug Administration to permit use
of their vaccine.
China and Russia have both deployed their own vaccines at home
and overseas. Chinese authorities have inoculated nearly one
million Chinese people with a vaccine from one state company,
though it has yet to provide solid clinical evidence of its
efficacy. Russia has said its own homegrown vaccine has an efficacy
rate of above 90%.
The AstraZeneca-Oxford vaccine stands out among the leading
Western candidates. The partners committed to selling it without
profit during the pandemic and promised to distribute it across a
much wider geographic footprint, including in large parts of the
developing world. The shot is expected to cost $3 to $5 a dose
globally during the pandemic.
The shot was created from a more traditional vaccine methodology
than the gene-based technology used by Moderna and Pfizer. The
Oxford-AstraZeneca shot doesn't need to be stored in subzero
temperatures, making its rollout easier, researchers and logistics
Participants in the trials are 18 years or older with stable
underlying medical conditions. There were 131 Covid-19 cases among
trial volunteers analyzed in the results. Researchers said that in
addition to showing positive results in stopping transmission of
the disease, the vaccine was effective in preventing severe
symptoms and hospitalizations -- a sought-after benefit to curb
Covid-19 deaths and stop hospitals from being overburdened.
AstraZeneca said it would seek emergency-use authorization from
the World Health Organization to distribute the vaccine in
low-income countries and prepare regulatory submissions to
authorities in countries that have early-approval programs.
Pending regulatory authorization, the shot could be available in
limited volumes by year-end, with hundreds of millions more doses
available each month after that, AstraZeneca executives said
Monday. The level of output depends on manufacturers across the
world that are working with AstraZeneca to produce the vaccine.
The European Medicines Agency, which authorizes new medicines
for sale in the European Union, said in early October that it had
begun a rolling review of the Oxford vaccine to speed up a
potential approval. A rolling review allows regulators to evaluate
preliminary data such as those from lab experiments before
final-stage clinical trials are completed.
Officials in the U.K., which is transitioning out of the EU, say
they have the power to authorize use of a Covid-19 vaccine in the
U.K. before year-end, if they choose. The U.K. also has been
reviewing Oxford and AstraZeneca's data on a rolling basis since
early November. Canada has also begun a rolling review of the
Monday's results are from trials held in the U.K. and Brazil.
Late-stage clinical trials of the vaccine are continuing in the
U.S. following a trial pause there that spanned most of September
The results released Monday were based on trials involving more
than 23,000 participants. Individuals who received the vaccine,
called AZD1222, received one of two combinations: a half dose
followed by a full dose, which showed to be 90% effective; or two
full doses, which were 62% effective. Researchers said Monday the
preliminary results were promising but will need to be fleshed out
before scientists can understand why the half-dose regimen was more
effective. They said more than 3,000 of the overall trial
participants received the half-dose regimen.
Oxford's chief investigator in the trials, Prof. Andrew Pollard,
said the results mean the vaccine "may be around 90% effective."
The regimen using a half dose for the first dose would also mean
more people could be vaccinated with planned supplies, he and
AstraZeneca executives said.
Prof. Sarah Gilbert, one of Oxford's lead scientists on the
vaccine, said researchers are digging into why the half-dose
regimen has shown to be more effective. She said it could be that
the lower first dose better mimics the natural human immune system,
coaxing the body to be ready for an eventual fight against the
virus in a way that makes the second, standard dose more
Two-dose vaccines often behave differently from single-dose
vaccines, Oxford scientists said. With the latter, a stronger dose
is usually closely matched with higher efficacy. With two doses,
the first dose acts as a prime for the second dose.
AstraZeneca will seek regulatory permission to alter its U.S.
trials as quickly as possible based on these results in order to
test more participants using the more-effective half-dose regimen,
executives said Monday. More than 10,000 people in the U.S. have
received the full-dose schedule, AstraZeneca said, adding that it
hopes to add the half-dose schedule within a matter of weeks. The
FDA must sign off on any new trial protocols and ultimately
authorize the shot's use in the U.S.
The differing trial time lines mean that the vaccine could be
available in the U.K., Europe and elsewhere before the U.S.
As trials continue, Oxford and AstraZeneca will continue to
refine the efficacy readings, helping determine whether the
more-positive results hold up across a broader population of
participants. The Oxford-AstraZeneca vaccine trials ultimately will
enroll as many as 60,000 participants globally. The U.K. drugmaker
said that the full analysis of the results is being submitted for
A full review of broader global trial results and full safety
data are still to come.
Some researchers also said that it will be important to compare
the effectiveness and safety of the leading vaccine candidates side
by side. Oxford and AstraZeneca officials said such comparisons are
difficult at this stage, but added that different shots are likely
to be effective in different people, which scientists expect to be
a positive for fending off serious Covid-19 symptoms and halting
the virus's spread.
Like with other Covid-19 vaccines in development, researchers
don't yet know how long the positive effects of the shot last,
which is key to understanding the required frequency of
vaccination. It will also affect overall effectiveness in
preventing the spread of the disease and helping jump-start
Oxford and AstraZeneca's vaccine uses a more traditional
approach than the Moderna and Pfizer shots, which both rely on a
new technology called messenger RNA to induce an immune response
inside the body. AstraZeneca's vaccine instead relies on
introducing a weakened, chimpanzee virus into the body to trigger
the immune response.
"A particular strength of this vaccine is that it can be stored
in a fridge," said Prof. Azra Ghani, chair in infectious disease
epidemiology at Imperial College London. "This means that it can be
distributed around the world using existing delivery
Oxford invented the vaccine along with a company spun out of the
university called Vaccitech Ltd. In April, Vaccitech relinquished
its rights to the vaccine to Oxford in exchange for a small slice
of potential future royalties, enabling Oxford's exclusive deal
In May, Oxford started Phase 2 and 3 human trials, and
AstraZeneca in late August launched a large, final-stage U.S. study
aiming to enroll 30,000 volunteers to test the vaccine. The study
was paused in early September after a patient in a U.K. trial
suffered from an unexplained illness. The FDA permitted the U.S.
study to resume Oct. 23. The separate, final-stage trial in the
U.K. also paused but was restarted within less than a week.
An independent safety committee determined the illness was
either unrelated to the vaccine, or couldn't be linked to the
vaccine because of a lack of information to determine a connection,
according to an information sheet given to study volunteers and
posted online by the University of Oxford.
Later, a participant in trials of the vaccine in Brazil died,
but the country's health regulator immediately said the trials
would continue. At the time, Oxford said it had carried out an
assessment of the case in Brazil and that there were no concerns
about the safety of the trial. An independent assessment of the
case didn't present any concerns, AstraZeneca said.
Write to Jenny Strasburg at firstname.lastname@example.org
(END) Dow Jones Newswires
November 23, 2020 09:47 ET (14:47 GMT)
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