| -Caveat Lector-
Here we go again! - JR
Government Considers New Smallpox Vaccine By Griff Witte Buoyed by promising results in animal experiments, government officials are
contemplating buying massive quantities of a new type of smallpox vaccine to
supplement the national stockpile already assembled in the aftermath of the
Sept. 11, 2001, attacks. Scientists believe that unlike any of the vaccines now available, the new
vaccine may be effective in protecting against the deadly infectious disease
without the risk of serious -- and occasionally lethal -- side effects. Efforts to develop the new vaccine, underway for several years, have taken on
an air of urgency after safety concerns stalled a 2003 campaign to vaccinate
millions of health care professionals and emergency workers who might be first
to respond to a biological attack. Those concerns were underscored on Tuesday,
when the vaccine that makes up the bulk of the U.S. stockpile was possibly
linked to cases of heart inflammation. As doubts grow about the existing vaccines, scientists are increasingly
optimistic about the prospects for the experimental vaccine, called Modified
Vaccinia Ankara, or MVA. Scientists say recently conducted studies using MVA on mice and monkeys
indicated the vaccine is both effective and safe, results that are especially
encouraging for the some 30 percent of the population that is not supposed to
take any of the vaccines now available because of a high risk of complications.
That group includes people with HIV, those with compromised immune systems due
to chemotherapy, pregnant women and individuals with the skin disease
eczema. But some government officials say MVA has shown such promise that it could do
far more than merely fill the gaps left by other vaccines, and that it may
become the nation's primary means of defense against a smallpox attack. They
say, too, that it could help resuscitate the foundering national campaign to
vaccinate millions of emergency workers who would be responsible for cutting off
the deadly virus's spread in the event of an outbreak. "As of now, the front-line vaccine we have is Dryvax," said Anthony S. Fauci,
director of the National Institute of Allergy and Infectious Diseases, referring
to the only vaccine now licensed for smallpox. "The question is whether we find
something that comes along that can replace it. That's looking like it could be
MVA." But to get to that point, the cost of producing the drug would be well into
the hundreds of millions of dollars, if not the billions. That sum is too high,
some public health experts say, especially given that scientists may not know
whether MVA truly works until there's an attack. Unlike Dryvax, which was used
effectively during a global eradication campaign during the 1970s, MVA has never
been put to the test during an outbreak. Most experts believe the probability of a smallpox attack is low. Following
eradication, only two known stocks of the virus remained in the world: one at
the Centers for Disease Control and Prevention in Atlanta, and another in
Russia. Vaccination campaigns in the United States ended decades ago because the
risk of the vaccine was considered greater than that of the virus. But national security experts fear that some of the Russian stockpile could
be in the hands of terrorists. Smallpox is one of the most potent bioterror
agents because it spreads from person to person and because it kills 30 percent
of its victims while permanently disfiguring many of the rest. After the 2001 anthrax attacks, the federal government made it a priority to
develop a stockpile of smallpox vaccine large enough for every man, woman and
child in the country. Now the question is whether a second stockpile of safer
vaccine is needed, and if the government can afford it. "The cost is unknown. But that has to be factored in," said D.A. Henderson, a
science adviser to the Department of Health and Human Services and one of the
principal forces behind smallpox's eradication. Henderson said that dose for dose, MVA will end up being significantly more
expensive than any of the smallpox vaccines now available because a lot more of
the vaccine will likely be needed to induce immunity. The current stockpile consists of three vaccines, including Dryvax from the
government's decades-old stockpile. The second was donated from the stockpiles
of Aventis Pasteur, the French vaccine maker. The third, made by Acambis PLC, is
an update of Dryvax using modern production techniques. They all protect people using the same basic method, one that dates back
centuries. Although the vaccines in the stockpile are produced in different
ways, they all involve a virus related to smallpox that, when injected, begins
to replicate vigorously and spurs the body's immunity. The replication of the
virus can have side effects, however, that range from the mild -- a fever or a
swollen arm -- to the serious -- an inflammation of the brain known as
encephalitis or, perhaps, an inflammation of the heart. MVA is also alive when it's injected, but it doesn't replicate well in humans
so researchers believe that it's much less likely to cause side effects. The
vaccine was first discovered in Turkey, and was later given to more than 100,000
people in Germany. Because Germany didn't have smallpox at the time, the vaccine's ability to
combat the disease remains unknown. But in U.S. government studies completed
earlier this year on animals, the vaccine surpassed experts' expectations. In one experiment, monkeys were given Dryvax, MVA or no vaccine at all. They
were then bombarded with monkeypox, a close cousin of smallpox. The monkeys that
had not been immunized died, while all of those that had been immunized by
either of the vaccines lived. Bernard Moss, who conducted the experiments for
Fauci's NIAID, said he was impressed with how well the MVA-immunized monkeys
held up to the challenge. "We were very gratified. They showed absolutely no signs of illness," he
said. A second study tested MVA's effectiveness with mice whose immune systems had
been compromised. Again, MVA did the job without causing adverse reactions.
Future studies are intended to determine how quickly the protection takes
effect, and how long it lasts. The vaccine is scheduled to enter human trials in the United States within
weeks, using samples from two competing companies. One of those companies,
Acambis, has already produced an updated version of Dryvax called ACAM2000, some
200 million doses of which have been purchased in the past few years by the
government. The company stopped adding volunteers to a study on ACAM2000 this
week, however, after at least one person exhibited swelling in the heart.
Acambis officials declined to comment on their MVA program. The other company is the Danish firm Bavarian Nordic AS. The two companies
are vying for a contract to produce several million doses of MVA that will
likely be awarded later this year. Another contract, calling for 60 million
doses or more, is slated to go out to bid in the fall. Last year, the
Congressional Budget Office estimated such a purchase would cost $900
million. Bavarian Nordic chief executive Peter Wulff said that, at least initially,
government officials are looking at MVA as a niche vaccine for those who can't
take one of the other vaccines because of the threat of complications. He
thinks, however, the government will eventually want to use MVA for everyone.
"If you have something that is safe, why would you want to use something that
is unsafe?" Wulff said. Bavarian Nordic and Acambis are not the only companies hoping to produce the
vaccine of the future, and MVA isn't the only contender for that title. In the
long term, experts say that a genetically engineered vaccine may be the
solution. In the shorter term, the California-based biotechnology firm VaxGen
Inc. reported this week that its vaccine, known as LC16m8, protected rabbits and
mice against a pox virus just as well as Dryvax after only one dose. Scientists
have yet to determine how many doses of MVA are needed to induce immunity. The
question is important because in the event of an attack, there may not be time
for more than one dose. "MVA would have little utility in response to an
outbreak," said VaxGen chief executive Lance K. Gordon. Some worry, too, that MVA may not be available for several years, and that
focusing on it so heavily may distract from the more immediate goal of getting
emergency workers immunized with Dryvax. "We have a misperception of risk with the existing vaccine," said William
Bicknell, professor of international health at Boston University and a former
Massachusetts health commissioner, who insists Dryvax is safe for healthy
adults. "MVA would be even safer. So much the better. But MVA is still several
years away and waiting is not the best idea." Fauci said he believes MVA could be in the stockpile within a year or two,
and that it may ultimately be used to immunize health care workers who had been
reluctant to get a shot of Dryvax. Before the vaccine can be licensed for use by the Food and Drug
Administration, however, it has to undergo a full battery of human trials.
Approval of any smallpox vaccine is complicated by the fact that researchers
can't ethically expose humans to the disease. Up until now, the best they could
do was to give the vaccine to humans to check for side effects, and then test
the vaccine's effectiveness on monkeys using monkeypox. But Peter Jahrling,
principal scientific adviser with the U.S. Army Medical Research Institute of
Infectious Diseases, said he could take those efforts a step further by exposing
monkeys to actual smallpox. "I would be very surprised if it didn't work," Jahrling said. "But the only
way to know is to do it, and I'll do it if asked." Staff writer Justin Gillis contributed to this report.
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