Drugmakers are working as quickly as possible to develop a vaccine to
combat the rapidly spreading coronavirus that has infected more than
100,000 people worldwide.
Behind the scenes, scientists and medical experts are concerned that
rushing a vaccine could end up worsening the infection in some patients
rather than preventing it.
Studies have suggested that coronavirus vaccines carry the risk of
what is known as vaccine enhancement, where instead of protecting
against infection, the vaccine can actually make the disease worse when a
vaccinated person is infected with the virus. The mechanism that causes
that risk is not fully understood and is one of the stumbling blocks
that has prevented the successful development of a coronavirus vaccine.
Normally, researchers would take months to test for the possibility
of vaccine enhancement in animals. Given the urgency to stem the spread
of the new coronavirus, some drugmakers are moving straight into
small-scale human tests, without waiting for the completion of such
animal tests.
“I understand the importance of accelerating timelines for vaccines
in general, but from everything I know, this is not the vaccine to be
doing it with,” Dr Peter Hotez, dean of the National School of Tropical
Medicine at Baylor College of Medicine, told Reuters.
Hotez worked on development of a vaccine for SARS (Severe Acute
Respiratory Syndrome), the coronavirus behind a major 2003 outbreak, and
found that some vaccinated animals developed more severe disease
compared with unvaccinated animals when they were exposed to the virus.
“There is a risk of immune enhancement,” said Hotez. “The way you
reduce that risk is first you show it does not occur in laboratory
animals.”
Hotez testified last week before the U.S. House Committee on Science,
Space and Technology about the need for sustained funding for vaccine
research. There remains no vaccine for any of the new coronaviruses that
have caused outbreaks in the past 20 years.
At least for now, the world’s experts have concluded that accelerated testing is a risk worth taking.
At a specially convened World Health Organization (WHO) meeting in
mid-February, designed to co-ordinate a global response to the new
coronavirus, scientists representing government-funded research
organizations and drugmakers around the world agreed that the threat was
so great that vaccine developers should move quickly into human trials,
before animal testing is completed, four people who attended the
meeting told Reuters.
“You want to have a vaccine as quickly as possible,” Dr Marie-Paule
Kieny, former assistant director-general at the WHO, who co-chaired the
meeting, told Reuters. “You have to balance this with the risk that you
impose on a very small number of people, and do all you can do to
mitigate this risk as much as possible.”
The conclusion of that meeting, which was not open to media, has not
been officially publicized by the WHO. It does not reflect any official
position adopted by the WHO, a United Nations body whose job it is to
help shape global health policy.
Regulatory oversight of drugmakers and medical research is in the
hands of national regulators. The most powerful of those, the U.S. Food
and Drug Administration (FDA), has signaled that it is in agreement with
the consensus and will not stand in the way of accelerated testing
schedules.
“When responding to an urgent public health situation such as novel
coronavirus, we intend to exercise regulatory flexibility and consider
all data relevant to a certain vaccine platform,” FDA spokeswoman
Stephanie Caccomo said in a statement. The agency had no comment
specifically on animal testing for vaccine enhancement.
Coronavirus vaccine developers are still required to conduct routine
animal testing to make sure the vaccine itself is not toxic and is
likely to help the immune system respond to the virus.
SEATTLE RISK
Some 20 coronavirus vaccine candidates are being developed by
research institutes and drugmakers including America’s Johnson &
Johnson and France’s Sanofi SA. The U.S. government has earmarked more
than $3 billion for coronavirus treatments and vaccines.
Biotechnology company Moderna Inc, which is working with the
U.S.-funded National Institutes of Health (NIH), is the closest to human
testing, announcing plans to start a trial with 45 people in Seattle
this month.
Testing for the specific risk of vaccine enhancement in animals will
proceed simultaneously with human trials, the NIH told Reuters, which it
said should establish whether it is safe to expose larger numbers of
people to the vaccine. Moderna did not respond to requests for comment.
The plan is consistent with the WHO consensus and FDA requirements,
said Dr Emily Erbelding, director of the Division of Microbiology and
Infectious Diseases of the National Institute of Allergy and Infectious
Diseases (NIAID), part of the NIH. The trial is expected to take 14
months, a spokeswoman for the NIH said.
Dr Gregory Poland, a virologist and vaccine researcher with the Mayo
Clinic in Rochester, Minnesota, expressed doubts about that approach.
“This is important, but it has to be done in a way that reassures
scientists and the public that these (vaccines) are not only
efficacious, but safe,” he told Reuters.
Hotez said he was surprised human trials were going ahead. “If there
is immune enhancement in laboratory animals vaccinated with the Moderna
vaccine, that’s a showstopper,” he said.
U.S. immunotherapy company Inovio Pharmaceuticals Inc, which is
developing a coronavirus vaccine in collaboration with a Chinese
company, also expects to start human clinical trials in 30 U.S.
volunteers in April rather than wait for animal studies on vaccine
enhancement.
“The community as a whole weighed that and said we don’t want to
delay the clinical process. We’ve been encouraged to go as rapidly as
possible into Phase 1 studies,” Inovio Chief Executive Joseph Kim told
Reuters.
The company plans to start human safety trials shortly thereafter in
China and South Korea – two countries that have been hit hard by the
virus. Kim said he expects to have an answer to the question of vaccine
enhancement at some point this year.
The Moderna/NIH trial is enrolling patients at the Kaiser Permanente
Washington Health Research Institute in Seattle. The choice of location,
made several weeks ago, could prove to be problematic.
To reduce the risk to volunteers, scientists at the WHO meeting
recommended that drugmakers restrict early clinical trials to small
groups of healthy people and conduct them in places where the virus is
not spreading, according to Kieny, who now works at French research
institute Inserm. That lowers the chances that people who get the
vaccine could encounter the virus and trigger a more severe reaction.
Since the location was chosen, the Seattle metro area has emerged as
the epicenter of infections in the United States. Washington state has
reported 162 coronavirus infections and 22 deaths, out of a total of 755
infections and 26 deaths in the country as of Tuesday, according to a
tally by Johns Hopkins University.
Nevertheless, Moderna and the NIH plan to go ahead.
“We think there is no reason to have to change the site. If you
change it, there might be community transmission in another site over
the next couple of weeks,” Erbelding said. “Any risk of that to
participants is very small. It would be manageable as the trial
progresses. People are being observed very, very carefully.”
EARLY WARNING SIGNS
Tragic lessons from other vaccines and prior work on coronaviruses have raised some warning flags for developers.
The best-known example occurred in a U.S. trial in the 1960s of a
vaccine created by the NIH and licensed to Pfizer Inc to fight
respiratory syncytial virus (RSV), which causes pneumonia in infants.
The vast majority of babies who received the vaccine developed more
severe disease, and two toddlers died. A more recent example occurred in
the Philippines, where some 800,000 children were vaccinated with
Sanofi’s dengue vaccine, Dengvaxia. Only afterward did the company learn
that it could increase the risk of more severe disease in a small
percentage of individuals.
Research, including that conducted by Hotez, has shown that
coronaviruses in particular have the potential to produce this kind of
response. But testing for the risk of vaccine enhancement is
time-consuming because it requires scientists to breed mice that are
genetically altered to respond to the virus like humans. Work on these
and other animal models is just getting under way in several
laboratories around the world.
Moderna, Inovio and several other vaccine developers are not waiting
for that process to be completed and are planning to launch human trials
in record time for a virus that was only discovered in December.
Both Moderna and Inovio say their vaccines are likely to have a lower
risk of vaccine enhancement because they are made using newer
technology that focuses on specific genes on the outer ‘spike’ portion
of the virus. Coronavirus vaccines that caused vaccine enhancement were
typically made using an inactivated version of the entire virus. Neither
company has produced a licensed vaccine to date.
J&J said it is developing animal models to test for vaccine
enhancement and hopes to have a vaccine candidate ready for human trials
in October. A Sanofi spokeswoman said the company will examine this
risk before testing the vaccine in clinical trials.
“People know how traumatic the RSV experience was,” said Dr Johan Van
Hoof, global head of Janssen Vaccines, J&J’s vaccine unit. “When
you see signals in animals like this, we should not ignore them.”
https://www.reuters.com/article/us-health-coronavirus-vaccines-insight/as-pressure-for-coronavirus-vaccine-mounts-scientists-debate-risks-of-accelerated-testing-idUSKBN20Y1GZ