Last checked at 
(Adds quotes, details)
By Kate Holton and Josephine Mason
LONDON, Nov 23 (Reuters) - Britain’s AstraZeneca
said on Monday its vaccine for the novel coronavirus could be
around 90% effective without any serious side effects.
The vaccine developed by Oxford University was 90% effective
in preventing COVID-19 when it was administered as a half dose
followed by a full dose at least one month apart, according to
data from the late-stage trials in Britain and Brazil.
No serious safety events related to the vaccine have been
confirmed and it was well tolerated across both dosing regimens,
it said.
"This vaccine's efficacy and safety confirm that it will be
highly effective against COVID-19 and will have an immediate
impact on this public health emergency," Pascal Soriot, Astra's
chief executive, said in a statement.
The overall effectiveness was lower when measured across
different dosing regimes, giving an apparent initial advantage
to rival vaccines from Pfizer and Moderna. But scientists also
noted there may be advantages to AstraZeneca's vaccine.
"Importantly, from what we have heard the vaccine seems to
prevent infection not just disease. This is important as the
vaccine could reduce the spread of the virus as well as protect
the vulnerable from severe disease," said Peter Horby, a
professor of emerging infectious diseases and global health at
the University of Oxford.
He also noted that the Oxford vaccine "can be stored in the
fridge, as opposed to the freezer like the other two vaccines,
which means it is a more practical solution for use worldwide.”
The British drugmaker's preliminary trial results mark a
fresh breakthrough in the fight against a pandemic that has
killed nearly 1.4 million people and roiled the global economy.
British Prime minister Boris Johnson said it was "incredibly
exciting news the Oxford vaccine has proved so effective in
trials".
AstraZeneca shares fell 1.1% in early morning trade, defying
expectations for a bounce and underperforming the wider market
with the FTSE 100 index rising 0.5% at the open, as traders
perceived the efficacy data as disappointing compared with
results from rivals.
Efficacy fell to 62% when the vaccine was given as two full
doses at least one month apart. The combined analysis from both
dosing regimens resulted in an average efficacy of 70%. All
results were statistically significant.
The interim analysis was based on 131 infections among
participants who received the vaccine and those in a control
group who were given an established meningitis shot.
While the efficacy reading from Astra's viral vector vaccine
is lower than its U.S. rivals, the data will boost confidence
about the chances of successfully developing a variety of
vaccines using different approaches. Public health experts say
the world will need many vaccines to meet global demand.
On Nov. 16, U.S.-based Moderna Inc said its
experimental vaccine proved to be 94.5% effective based on an
early data analysis.
A week earlier, Pfizer Inc and Germany's BioNTech SE
said their vaccine candidate had demonstrated
greater than 90% efficacy that rose to 95% with analysis of full
trial data.
Russia's Sputnik-V vaccine on Nov. 11 was also shown to be
more than 90% effective, though only based on 20
infections.
The AstraZeneca vaccine uses a modified version of a
chimpanzee common cold virus to deliver instructions to cells to
fight the target virus, which is different than the new
technology known as messenger RNA (mRNA) deployed by
Pfizer/BioNTech and Moderna.
The Astra vaccine does not require ultra-cold storage which
may make it easier to administer than the Pfizer-BioNTech shot,
which needs to be refrigerated at -70 degrees.
The company - one of the UK's most valuable listed companies
- will now immediately prepare regulatory submission of the data
to authorities around the world that have a framework in place
for conditional or early approval.
It will also seek an emergency use listing from the World
Health Organization to speed up availability in low-income
countries. In parallel, the full analysis of the interim results
is being submitted for publication in a peer-reviewed journal.
(Reporting by Kate Holton in London and Josephine Mason; Aakash
Jagadeesh Babu in Bengaluru; Editing by Guy Faulconbridge,
Christopher Cushing and Peter Graff)
