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By Julie Steenhuysen
CHICAGO, Dec 7 (Reuters) - A top U.S. scientist overseeing
COVID-19 vaccine trials expects a large U.S. study to determine
how effective AstraZeneca's experimental inoculation is,
following perplexing results from other trials released by the
company and partner Oxford University.
AstraZeneca Plc is one of the leading vaccine
developers, but interim data released Nov. 23 from trials in
Britain and Brazil showed a vastly divergent performance when
the vaccine was tested in two different dose
combinations.
According to the company, a small group of trial subjects
inadvertently received a half dose followed by a full dose,
instead of the planned two full doses. In that group, the
vaccine proved to be 90% effective at preventing illness. But
the larger group that received two full doses showed a 62%
success rate.
Although 62% efficacy is above the benchmark set by
regulators to declare a COVID-19 vaccine a success, it pales
when compared with efficacy of 95% and 94.1% demonstrated in
large trials for vaccines from Pfizer Inc and Moderna
Inc, respectively.
A U.S. study of AstraZeneca's vaccine involving some 30,000
volunteers is in the works and should produce data by late
January.
"We feel very comfortable that we designed a really good
trial in the United States, where everybody's getting boosted in
a uniform time, and we know what the dose is," said Dr. Larry
Corey, co-leader of the U.S. Coronavirus Vaccine Prevention
Network, who helped design and is overseeing trials for the U.S.
government Operation Warp Speed program.
The dosing in the British trial "wasn't done correctly,"
Corey maintains. Still, the dosing difference does not fully
explain the variation in effectiveness seen in the UK and
Brazilian trials, he said.
"One of the issues with the Oxford data is that there's a
lot of lack of uniformity in the schedule and the dose that
makes interpretation of the results difficult at best," he said
in a phone interview.
There were also differences in the intervals between doses
in the UK trial versus the Brazilian trial, as well as
significant differences in the age range included in the
studies. For example, everyone in the 90% effective group was
under the age of 55, a group less susceptible to severe
COVID-19.
"My personal summation is that there seems to be
effectiveness in the AstraZeneca vaccine from this other trial
that provides optimism that the current trial in the United
States will define that effectiveness," he said.
Moncef Slaoui, chief adviser for the Operation Warp Speed
vaccine program, said last week the British and Brazilian trials
may not be enough to ensure the vaccine receives a U.S. Food and
Drug Administration emergency use authorization.
Results and potentially a request for U.S. emergency use
authorization by AstraZeneca could come in late January, he
said.
AstraZeneca has said it is considering a new global trial
based on the half dose first regimen.
The U.S. trial calls for testing the original regimen of two
full doses.
Should AstraZeneca decide to run a new U.S. trial testing
the half dose first option, Corey said, the United States was
unlikely to help foot the bill.
"Companies get to decide what they want to do," he said.
"I'm sure they'll have to fund it themselves, or maybe somebody
else would fund it for them."
(Reporting by Julie Steenhuysen; Additional reporting by Marisa
Taylor in Washington; Editing by Peter Henderson and Bill
Berkrot)
