[After reporting strong antibody levels in Phase 2 trials, Moderna and Pfizer in recent days announced preliminary Phase 3 efficacy rates above 90 percent, a result greeted with enthusiasm from the medical world. (For their experimental coronavirus vaccines, Moderna is partnering with the National Institutes of Health and Pfizer is working with German biotechnology firm BioNTech.)]
By Eva Dou
While
the vaccine appeared to be safe in these early clinical trials, the company
reported that it generated lower levels of protective antibodies in the
bloodstream compared with those arising in recovered coronavirus patients. In
comparison, Moderna and Pfizer, which have separate experimental vaccines, had
reported antibody levels on par with or higher than those produced in recovered
coronavirus patients.
These
early results put Sinovac on the back foot to prove its vaccine is effective in
ongoing Phase 3 trials.
“That
is a concern,” said Thomas Campbell, associate dean for clinical research at
the University of Colorado, of the low antibody levels in Sinovac’s Phase 2
trial. “It’s an important point here, in terms of comparing this vaccine to,
for instance, the Moderna and Pfizer vaccines.”
[As
the world awaits a coronavirus vaccine, some in China get early doses]
Indonesia,
the world’s fourth-most populous country, recently made a big bet on Sinovac’s
vaccine as officials grapple with a severe coronavirus outbreak. In an interview with Reuters on Friday, President Joko
Widodo said the government had sought emergency authorization from the
country’s food and drug agency to roll out the vaccine by the end of the year.
In its study published Tuesday in the peer-reviewed journal the Lancet, Sinovac wrote that despite the lower antibody levels, it believed its vaccine would prove effective. For other coronavirus strains, lower antibody levels have still conferred immunity, it said.
Whether
this will be the case this time is being tested in Sinovac’s Phase 3 trials
underway in Indonesia, Brazil and Turkey.
After
reporting strong antibody levels in Phase 2 trials, Moderna and Pfizer in recent days announced preliminary Phase 3 efficacy
rates above 90 percent, a result greeted with enthusiasm from the medical
world. (For their experimental coronavirus vaccines, Moderna is partnering with
the National Institutes of Health and Pfizer is working with German
biotechnology firm BioNTech.)
A
Sinovac spokesman said Wednesday that the company could not immediately release
its own preliminary Phase 3 efficacy rate, as not enough cases of the
coronavirus have emerged yet in its study population.
“For
Phase 3 preliminary analysis of results, we need to accumulate a certain number
of cases for the data analysts to carry out their analysis,” the Sinovac
spokesman said in a statement to The Washington Post. “We don’t have this data
yet so we can’t yet reply.”
Campbell
said Moderna and Pfizer were able to provide early Phase 3 results, in part,
because of the escalating coronavirus outbreak in the United States,
which has resulted in enough cases among those enrolled in their study for
statistical analysis.
[China
and Russia are ahead in the vaccine race, bending rules as they go]
While
Sinovac had announced a few results from its Phase 1 and Phase 2 trials over
the summer, calling them a success, the peer-reviewed study this week was the
first time it provided data and details.
Sinovac’s
Phase 1 trial began in April with 144 participants, and its Phase 2 trial began
in May with 600 people. Participants ranged in age from 18 to 59 and were
recruited from a single county of China’s southern Jiangsu province.
In Sinovac’s Phase 1 trial, 23 of the 96 who received vaccines reported side effects, which Sinovac said were mostly mild, such as pain at the site of injection. It said one person had a severe reaction of hives and recovered within three days with treatment.
In
the Phase 2 trial, participants were quick to produce antibodies in response to
the vaccine injection, but antibody levels remained below the measurements in
recovered patients.
Liu
Yang in Beijing contributed to this report.
Read
more
As
the world awaits a coronavirus vaccine, some in China get an early dose
China
and Russia are ahead in the global vaccine race, bending long-standing rules as
they go
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