- As the US government gears up for production of a new
supply of smallpox vaccine, federal scientists said they also are
fast-tracking
development of the world's first ebola vaccine and should be ready to test
it on an initial 20 Americans before next summer.
-
- The vaccine, which is actually a combination of a primary
and a booster vaccine, has been tested in small animals and monkeys for
safety and effectiveness during the past two years. But after Sept. 11,
researchers decided to expedite safety testing in a small number of humans,
called phase 1 trials, at the National Institutes of Health clinical
testing
site in Maryland.
-
- Like smallpox, ebola is considered a ''category A,''
or high priority, agent by the Centers for Disease Control, meaning that
it poses the highest level of risk to national security because it's very
contagious, often fatal, has the potential to cause public panic, and
requires
special preparations for an outbreak.
-
- The disease is native to the African continent, where
since the first identified outbreak in Zaire in 1976 it has killed hundreds
of people. There never has been a case in the United States, but Dr. Gary
Nabel, who is leading the research effort at the NIH, said Russian
scientists
are known to have researched weaponizing ebola in the former Soviet Union.
And the 1995 book ''The Hot Zone,'' which chronicled the disease's
horrifying
symptoms and its mysterious spread through Africa, became a bestseller
here and made ebola an American household word.
-
- Because the disease does not occur in the United States
naturally, testing and manufacturing a vaccine will be tricky both
ethically
and financially.
-
- Safety testing can be performed on humans. But to truly
determine the vaccine's effectiveness, researchers must compare what
happens
when vaccinated people and nonvaccinated people, called the control group,
are exposed to the virus. It would be unethical to purposely expose
unprotected
people to ebola, and researchers cannot count on a naturally occurring
outbreak in the United States.
-
- Ethical problems also might arise if the vaccine seemed
very promising and researchers refused to vaccinate a control group,
instead
giving them a placebo during an actual outbreak.
-
- Nabel, who began developing the vaccine during a prior
job at the University of Michigan, said he's considering two alternatives:
Vaccinate a group of animal handlers in various countries who might be
exposed to the virus during the course of their work, or vaccinate some
health care workers in regions of Africa where a future outbreak is
possible
but is not underway.
-
- ''I think we could in good conscience approach people
who work in those hospitals and say, `You're at risk. We have a vaccine
candidate. We'd like to enroll you in a trial,''' said Nabel, director
of the NIH's vaccine research center. ''A good portion of those people
will never see the virus.''
-
- If there's an actual outbreak here before trials are
completed, researchers may have to rely instead on the results of testing
in animals. Four vaccinated monkeys were completely protected against the
virus, Nabel and his colleagues reported in scientific journals last
year.
-
- Dr. Donald Burke, director of the center for immunization
research at Johns Hopkins University, said efficacy testing in humans may
be impractical. Africa is so large that it may be impossible to predict
the next outbreak and immunize workers in that region, he said. An even
bigger problem than testing, Burke said, will be finding a company to
manufacture
the vaccine.
-
- ''No one is going to want to make this because it's not
going to make any money,'' he said.
-
- The typical start-up cost for vaccine production,
including
building a plant, perfecting manufacturing techniques, and training
employees,
is $300 million to $400 million, he said. And once a company invests the
money to make the ebola vaccine, it cannot count on continued long-term
production. The vaccine may be needed only if there is a terrorist attack
using the virus, an unlikely event.
-
- The manufacturer could try selling the vaccine to African
countries, but they don't even have money to buy vaccines for more
widespread
diseases such as measles. ''That is a terrible disincentive for a
manufacturer,
to make a vaccine needed in poor countries and not market it there and
then have the social pressure to produce it for them,'' Burke said.
-
- One solution, he said, is for the government or a private
foundation to fund the project. The Gates Foundation, for example, has
invested in seven orphan vaccines, including $150 million for the
development
of an AIDS vaccine and $50 million for a malaria vaccine, although none
of these vaccines have progressed to the manufacturing stage.
-
- Nabel said it's too soon to know which companies would
be interested in taking on the project or the cost of production. For the
trial, the University of Michigan and a California biotechnology company,
Vical, have agreed to make limited amounts of the vaccine.
-
- The vaccine comes in two parts. The primary shot is a
DNA vaccine that consists of proteins from all three strains of the ebola
virus. Since it is not a live virus vaccine, like the smallpox vaccine,
it cannot give a person ebola. And, the side effects are expected to be
minimal, such as irritation at the site of the shot, Nabel said.
-
- The booster shot is made from a weakened form of the
adenovirus, which typically causes respiratory infections. This has the
potential for more side effects, such as fever at high doses, and will
require more extensive human safety testing.
-
- Nabel said his center expects to file an investigational
new drug application with the Food and Drug Administration early next year
and apply to a review board for permission to do human testing. After the
applications are filed, he expects approval to take about a month.
-
- ''We want to move quickly,'' he said. ''We want to be
prepared. But we also need to do things safely. Right now there is no ebola
outbreak, so we don't want to rush it so much that harm is done.''
-
- ___
-
- Liz Kowalczyk can be reached by e-mail at
kowalczyk@globe.com.
-
- This story ran on page B1 of the Boston Globe on
11/22/2001.
- © Copyright 2001 Globe Newspaper Company.
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