How drugmakers can keep their pledge and still deliver an October
vaccine surprise
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[September 09, 2020]
By Michael Erman and Julie Steenhuysen
NEW YORK (Reuters) - As questions mount
over whether the United States will authorize a coronavirus vaccine
ahead of November elections, experts say there is a slim chance that
enough evidence will be available to prove one is safe and effective in
that time frame.
U.S. President Donald Trump has repeatedly said a vaccine is possible
before the Nov. 3 election, and accused a “deep state” within the
nation’s top health regulator of trying to slow pivotal clinical trials
to hamper his chances at a second term.
The U.S. Food and Drug Administration refuted that claim, saying its
decisions will be guided by data alone. Drugmakers, seeking to bolster
public confidence amid political squabbles on Tuesday pledged to uphold
scientific safety and efficacy standards in their quest for a vaccine.
However, comments from companies suggest they could have an answer on
whether their vaccines work within that time frame.
"It would really be an amazing vaccine to show that," Dr. Anthony Fauci,
director of the National Institute of Allergy and Infectious Diseases,
told Reuters.
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Fauci said initial trial results are likely to become available in
November or December, but late October remains a possibility. "It is
conceivable that if there are enough infections documented early on that
you might get that answer earlier," he said.
Vaccines must demonstrate they are at least 50% more effective than a
placebo to be considered for approval. To prove that, government
officials have said, at least 150 COVID-19 infections must be recorded
among trial participants with at least twice as many occurring among the
placebo group.
If a vaccine is especially effective, companies could have their answer
sooner. Pfizer Inc and Moderna Inc, whose U.S. vaccine trials have
enrolled thousands of people and are the most advanced, say they may
have proof after just a few dozen subjects become infected.
Independent panels of experts called data and safety monitoring boards (DSMB)
will review trial data at pre-specified points. These boards can
recommend companies stop the trials if the evidence is overwhelmingly
positive or negative.
For Pfizer, the first interim look occurs when 32 trial volunteers get
infected.
Experts interviewed by Reuters cautioned that information gleaned from a
limited number of subjects could miss important safety issues that
letting the trial fully play out might reveal.
'ABSOLUTELY INSUFFICIENT'
Pfizer's trial calls for four interim analyses by the DSMB, the first
after just 32 recorded infections. "We may have enough data to be able
to share the first analysis by October," said Pfizer spokeswoman Jerica
Pitts.
Moderna’s first interim analysis will come after 53 trial subjects
become infected, the company told investors last month.
Basing a decision on 53 cases, is “an absolutely insufficient number,”
said Dr. Gregory Poland, a vaccine researcher at the Mayo Clinic in
Rochester who has served on FDA vaccine advisory panels. "You would know
very little about safety."
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Small bottles labeled with a "Vaccine COVID-19" sticker and a
medical syringe are seen in this illustration taken taken April 10,
2020. REUTERS/Dado Ruvic/File Photo
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To halt the trials due to positive results, vaccines would likely
have to exceed the 50% efficacy threshold.
Pfizer has not disclosed what standard will be used for stopping its
trial early. William Gruber, head of vaccine clinical research and
development for Pfizer, said "the standard would be evidence of very
high efficacy."
A senior official with the U.S. effort to accelerate COVID-19
vaccine development said companies have created appropriate trials
to hold interim analyses that could detect especially effective
vaccines earlier.
SPEEDY ENROLLMENT
Although both drugmakers began vaccinating people in their
respective 30,000-subject trials on July 28, Pfizer is in position
to generate results earlier in part because it is administering the
second shot of its two-dose vaccine a week earlier than Moderna.
Moderna also slowed enrollment to ensure greater participation of
at-risk minorities in its study.
Pfizer's trial also begins collecting data on infections that occur
a week after it administers its second shot. Moderna has a two-week
lag between the second shot and when it will begin collecting
infection data in earnest.
Both trials are on pace to be fully enrolled soon.
Dr. Henry Miller, a senior fellow at the Pacific Research Institute
think tank and former director of the FDA's office of biotechnology,
said an emergency use authorization based on a small number of
infections would not deliver an adequate answer on the safety of a
vaccine intended for use by millions of healthy people. Some side
effects could take four to six months to occur, he said.
Dr. Gregory Glenn, research chief for Novavax Inc, which is also
developing a coronavirus vaccine, said the October timeline remains
possible. But he believes Americans will likely be waiting longer.
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"I just think humility is a good thing right now," he said. "The FDA
set out some pretty strict criteria for success. So that's going to
take a pretty good vaccine to do that."
(Reporting by Michael Erman and Julie Steenhuysen; Editing by
Caroline Humer and Bill Berkrot)
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