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By William
Carlsen
A monkey virus linked to human cancers
may have contaminated the oral polio vaccine for years after
the U.S. government ordered manufacturers to remove it, according
to drug company documents.
The simian
virus SV40 had contaminated early polio vaccine given to millions
of Americans.
When health officials discovered in 1961
that SV40 caused malignant tumors in lab animals, they ordered
the virus eliminated from all future vaccine.
But internal memos from Lederle Laboratories,
the chief producer of polio vaccine in the United States,
indicate SV40 may not have
been completely removed.
According to one memo, SV40 was found
in three of 15 lots of the oral vaccine seven months after
the federal directive was issued in March 1961. Lederle released
the contaminated vaccine to the public anyway, the memo shows.
The documents also suggest that the company
failed to test the monkey- kidney seed strains used to make
the bulk polio vaccine for contamination, despite a written
warning from Dr. Albert Sabin, who developed the oral vaccine.
Lederle and the US government insist there
is no evidence that any contaminated vaccine was distributed
after the directive went into effect.
Scientists discovered SV40 in the Salk
polio vaccine in 1960. By then as many as 30
million Americans
had been given injections of the SV40-tainted polio vaccine,
which was first licensed in 1955.
In recent years more than 60 scientific
studies have found SV40 in rare human brain, bone and lung-related
cancers, the same kinds of tumors the virus caused in laboratory
animals. Some scientists believe SV40
may play a role in causing those cancers.
One of the biggest mysteries, however,
is why SV40 has been found in tumors removed from people who
never received the contaminated Salk vaccine.
Researchers have several theories for
how the virus could have spread from those infected through
the Salk vaccine: in transmission from mother to fetus or
through breast milk; through sexual activity or a flu-like
virus.
But the Lederle documents, which were
obtained by Philadelphia attorney Stanley Kops in litigation
not related to SV40, raise the possibility the virus might
have been transmitted by contaminated oral vaccine, licensed
for production in 1962.
The documents include:
- A November 1961 memo saying the virus
was found in three of 15 lots of vaccine. According to the
memo, Dr. Roderick Murray, head of the government's program
to ensure vaccine purity, allowed the lots to be released.
To comply with the removal order,
Lederle had switched from rhesus monkeys, which are natural
hosts for SV40, to African green monkeys, supposedly free
from SV40. However, the memo notes that SV40
was found in 10 percent of
the green monkeys.
- A letter from Sabin to Lederle in October
1962, warning that sufficient testing for SV40 contamination
had not been done on one of his strains of weakened polio
virus that formed the seed for bulk vaccine production.
- A confidential memo in 1979 from a
Lederle official stating: "It should be noted that
Lederle did not test the original Sabin seeds for extraneous
agents or neurovirulence since Dr. Sabin assured us that
this had been done."
- Another memo stating that Lederle did
not test the seed "since only 50 (milliliters) or less
of each seed were provided by Dr. Sabin."
The two memos added that testing was unnecessary
because later vaccine samples submitted for license were free
of SV40.
Kops also said that he had taken testimony
in 1998 from a top Lederle official who said the
company did not have the test results from many
of the vaccine lots.
"The vaccine manufacturers and the
government need to disclose what really happened," said
Kops. "Without the facts, (scientists) will continue
to look in the wrong places to explain how people were infected
with SV40 after 1961."
At a 1997 conference, however, a Lederle
representative outlined the series of tests the company uses
to detect SV40 contamination. The company also says that it
uses antiserum to neutralize any SV40 in the "master
seeds."
But it is not clear whether these procedures
were in place in the years after the US government issued
its directive.
Last year, a lawsuit was filed in Los
Angeles against Lederle by the parents of 2 1/2-year-old Alexander
Horwin who died of a brain tumor that later tested positive
for SV40. The suit claims that the tumor was caused by SV40
and that he became infected
through a 1997 oral polio vaccine.
Kops and attorney Donald MacLachlan represent
a New Jersey family that is considering a suit against vaccine
manufacturers.
In 1970, surgeons removed a large brain
tumor from 2-year-old Mark Moreno. He since has undergone
five more surgeries and now wears a protective helmet over
the large opening in his cranium where bone grafts never took.
Moreno, now 33, lives with his mother and requires daily assistance.
Recent tests show Moreno's tumor was riddled
with SV40, according to the lawyers.
Eileen Moreno, Mark's mother, believes
her son's brain tumor was caused by SV40 and that he was infected
through the oral polio vaccine in 1968.
Last year, two investigators from the
US Food and Drug Administration used genetic testing to examine
30 samples of bulk oral polio vaccine used in the United States
going back to 1972. They reported finding no SV40.
But the government has not used the genetic
tests to determine whether vaccine made prior to 1972 was
contaminated.
Dr. William Egan, deputy director of the
FDA's vaccine research branch, said testing went back only
to 1972 because those samples were the
only ones available to them. "There was nothing
sinister," he said.
MacLachlan said he finds it "incredible"
that the government hasn't
comprehensively investigated the possibility of SV40 contamination
of the oral vaccine.
Simian Virus
Q&A
Q:
How widespread is the SV40 infection?
A:
Scientists and government health officials don't know, because
no comprehensive studies have addressed the question. What
is known is that during the 1950s and '60s, at least 10 million
to 30 million Americans -- and more than 100 million people
worldwide -- were given SV40-contaminated polio vaccine. The
virus also has been found in people who did not receive contaminated
vaccine.
Q:
Can I be tested for SV40?
A:
An accurate blood test does not exist. Current antibody blood
tests can be inaccurate, scientists say, because they also
may detect the presence of closely related viruses, and SV40
may be present at such a low level that no antibodies are
produced. Researchers are working to create an effective test.
Q:
In which kinds of cancers has SV40 been found?
A:
The virus has been detected in rare cancers, including:
- Mesothelioma, a fatal tumor of the
membrane surrounding the lungs. Few cases were reported
prior to 1950, but the incidence has grown in the United
States to 2,000 to 4,000 cases a year, with greater incidence
in Europe.
- Brain cancers: Primarily ependymomas
and choroid plexus tumors, but also astrocytomas, glioblastomas,
medulloblastoma, and meningiomas. Fewer than 1, 000 cases
of these cancers are reported in the United States each
year.
- Bone cancers: Primarily osteosarcomas,
but also chondrosarcoma and giant cell tumors. These also
make up fewer than 1,000 cases annually.
For more information on SV40 and the polio
virus, please check the Internet at sfgate.com/chronicle/sv40/.
San
Francisco Chronicle July 15, 2001
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