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* Britain asks regulator to assess shot for rollout
* Philippines says it will secure millions of doses
* Experts raise doubts over robustness of trial results
* Astra CEO says likely to run an extra global trial
By Alistair Smout and Karen Lema
LONDON/MANILA, Nov 27 (Reuters) - Britain gave AstraZeneca's
COVID-19 vaccine a vote of confidence on Friday when it asked
its regulator to assess it for a rollout after experts raised
questions about trial data and the company said it may run
another study to gauge the shot's efficacy.
The UK government has secured 100 million doses of the
vaccine, developed by AstraZeneca and Oxford University,
the most supplies it has ordered of any shot to fight the
pandemic.
The British drugmaker expects 4 million doses to be
available in the country by the end of next month, and Health
Secretary Matt Hancock aims for a rollout to begin before
Christmas.
"We have formally asked the regulator to assess the
Oxford/AstraZeneca vaccine, to understand the data and determine
whether it meets rigorous safety standards," Hancock said.
"This letter is an important step towards deploying a
vaccine as quickly as safely possible."
Britain's Medicines and Healthcare products Regulatory
Agency (MHRA) started an accelerated "rolling review" of the
vaccine at the start of this month as data comes in on safety
and efficacy.
In the global race to develop vaccines against COVID-19,
AstraZeneca's candidate is viewed as offering one of the best
hopes for many developing countries because of its cheaper price
and ability to be transported at normal fridge temperatures.
Officials in the Philippines said on Friday they would
secure 2.6 million shots of the AstraZeneca shot - the country's
first supply deal for a COVID-19 vaccine - and were negotiating
a possible purchase of a further 1 million doses.
The announcements came despite some scientists raising
doubts about the robustness of results showing the shot was 90%
effective in a sub-group of trial participants who, by error
initially, received a half dose followed by a full dose.
AstraZeneca had released trial data on Monday that showed
its experimental vaccine prevented on average 70% of COVID-19
cases in late-stage trials in Britain and Brazil.
While the success rate was 90% in the sub-group, some
experts said the relatively small number of participants made it
harder to be confident in the findings.
AstraZeneca said the administering of the half dose in the
trial had been reviewed and approved by independent data safety
monitors and the UK regulator, adding that the regulator
publicly confirmed there was "no concern".
CEO Pascal Soriot said on Thursday, though, that the
drugmaker was likely to run an additional global trial to assess
the efficacy of its vaccine using the lower dosage.
CONFUSION 'PROBLEMATIC'
Pauline Londeix, co-founder of French drug transparency
group OT-Med, said the apparent confusion over the trial results
was "very problematic for public confidence in vaccines".
"It has largely to do with the race drugmakers are engaged
in currently, which leads them to present vaccine candidates in
the best possible way and not release full protocols and
results. It is the opposite of what is needed in our view."
Nonetheless, Britain's top science adviser said on Thursday
that the interim results showed the AstraZeneca vaccine was
successful.
"The headline result is the vaccine works and that's very
exciting," Patrick Vallance said during a news conference with
Prime Minister Boris Johnson.
Shares in AstraZeneca were down 0.8% at around 0830 GMT.
They have fallen about 7% since it reported the vaccine data on
Monday.
Only 2,741 volunteers were in the sub-group of the
AstraZeneca-Oxford trial that gave the 90% efficacy read-out, a
fraction of the tens of thousands in trials that resulted in the
above 90% efficacy data released earlier this month for
Pfizer-BioNTech's and Moderna's vaccines.
"Sub-group analyses in randomised controlled trials are
always fraught with difficulties," said Paul Hunter, a professor
of medicine at Britain's University of East Anglia.
"In order to have faith in the results," Hunter said, any
sub-group analysis "should be sufficiently powered" with large
numbers of volunteers to take readings from.
'NUMBER OF VARIABLES'
In contrast to AstraZeneca's stock price drop this week,
Moderna has rallied 22% since releasing its vaccine
trial data on Nov. 16 and Pfizer and BioNTech
are up 6% and 14% respectively since announcing their successful
data on Nov. 9.
The U.S. regulator, the Food and Drug Administration (FDA),
has not commented on AstraZeneca's vaccine trial results. The
European Medicines Agency said on Thursday it would "assess data
on the efficacy and safety of the vaccine in the coming weeks
once they have been received from the company".
Moncef Slaoui, chief scientific adviser for the U.S.
government's vaccine programme Operation Warp Speed, has also
highlighted gaps in the trial data.
He said no-one in the subgroup that got the initial half
dose was older than 55 - suggesting the regimen's efficacy in
crucial older age groups is unproven in this interim data.
In the group that received a correct full dose followed by a
full dose, he noted, older people were included.
"There are a number of variables that we need to understand,
and what has been the role of each one of them in achieving the
difference in efficacy," Slaoui told a briefing on Tuesday.
(Reporting by Alistair Smout in London and Karen Lema in
Manila; Additional reporting by Kate Kelland in London and
Matthias Blamont in Paris; Writing by Pravin Char; Editing by
Carmel Crimmins)
