Vaunted Ebola Vaccine Faces Questions
April 24 2017 - 6:51PM
Dow Jones News
By Thomas M. Burton and Michelle Hackman
The deadly Ebola outbreak in West Africa two years ago, the
worst in recorded history, led to a vaccine that seemingly would
stop the next Ebola epidemic in its tracks.
In December, doctors from the World Health Organization, Doctors
Without Borders and other groups reported in the British medical
journal The Lancet that a vaccine from Merck & Co. and NewLink
Genetics Corp. tested during the outbreak proved to be 100%
effective at preventing people from contracting the hemorrhagic
fever once the vaccine's protection kicked in.
Now there are questions about that claim. A panel of scientists
from the esteemed U.S. National Academy of Medicine has challenged
the methodology of that 4,160-patient trial in the African nation
of Guinea. They conclude the vaccine "most likely provides some
protection to recipients" but that protection "could in reality be
quite low."
"There is greater uncertainty about how effective this vaccine
is," said one of the National Academy authors, Kathryn Edwards,
chief of pediatrics and a vaccine specialist at Vanderbilt
University.
Merck and NewLink didn't immediately comment on the finding.
The finding is of great consequence. In the event of another
Ebola epidemic, a vaccine with modest usefulness may still prevent
deaths but not provide a total firewall. The last outbreak involved
28,616 Ebola cases, and led to more than 11,300 deaths.
The 287-page National Academy report tells the comprehensive
story of vaccines and drugs tried in West Africa. The drugs mostly
failed, and the Merck vaccine study remains the most important work
so far.
The National Academy is a private nonprofit organization that
serves as an advisory group to the U.S. government. The Ebola study
was sponsored by the National Institutes of Health, the Food and
Drug Administration and the U.S. Department of Health and Human
Services.
Those entities were parties to a fierce scientific debate that
erupted during the Ebola epidemic. Clinicians from groups like
Doctors Without Borders and Britain's University of Oxford argued
it was unethical to conduct a normal clinical study with patients
randomly assigned to a vaccine or a placebo. That is the gold
standard in science, but one that would exclude half of patients
from potentially preventive treatment. They contended it was
immoral to exclude villagers and health-care workers on the front
lines from the vaccine.
Doctors at the NIH, FDA and HHS countered that no one knew if
the vaccines and drugs worked or were harmful, so a randomized
study was essential.
On this question, the National Academy report was definitive:
"This committee found...that the randomized controlled trial was an
ethical and appropriate design to use, even in the context of the
Ebola epidemic."
But the Guinea vaccination trial was a compromise. Instead of
randomizing people, it randomized groups of people who had had
contact with an infected person. Researchers identified a ring of
human contacts in the area where Ebola broke out. In the first
ring, villagers were to be vaccinated right away. The next ring of
contacts, or "cluster," received a delayed vaccination after 21
days, the outside time period for someone to show Ebola symptoms.
That randomization was then expanded to more areas throughout
Guinea.
Estimating that a vaccine would take 10 days to be effective,
researchers counted Ebola cases that erupted 10 days or more after
the first case. In this analysis, there were no new Ebola cases in
the immediate-vaccination clusters, and 16 in delayed clusters;
hence, the 100% statement.
One of the Guinea vaccine-study researchers, Ira Longini of the
University of Florida, said in an interview, "Not a single
vaccinated person became ill after being vaccinated."
However, people did get ill in the first nine days after
vaccination. During that period, 20 of 3,232 participants got Ebola
in nine of 51 immediate-vaccination rings, versus 21 of 3,096 in
seven of 47 clusters randomized to receive delayed vaccination.
So there is agreement the vaccine works. But the National
Academy team concluded that varying ways of analyzing the data lead
to differing estimates of how effective the vaccine is.
One confounding issue is that there are indications that
exposure to the illness varied from town to town. "The small
proportion of clusters in which Ebola cases were reported raises a
concern about the comparability of risk across clusters," the panel
wrote.
Also, about one-third of the people assigned to immediate
vaccination didn't get vaccinated (some villagers declined) -- a
phenomenon that generally raises red flags in research. A concern
is that health-conscious people who got vaccinated had different
characteristics from the others, damaging the effort toward an
impartial study.
"The rules of science and research don't change during an
outbreak," said H. Clifford Lane, deputy director of the NIH's
National Institute of Allergy and Infectious Diseases. "The widely
publicized number of 100% was not based on the most rigorous
analysis of the data."
Write to Thomas M. Burton at tom.burton@wsj.com and Michelle
Hackman at Michelle.Hackman@wsj.com
(END) Dow Jones Newswires
April 24, 2017 18:36 ET (22:36 GMT)
Copyright (c) 2017 Dow Jones & Company, Inc.
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