- WASHINGTON (Reuters) - A
monkey virus that contaminated some batches of polio vaccine in the 1950s
and 1960s had the potential to cause cancer, but there is not enough evidence
to tell whether it actually did, a panel of experts reported on Tuesday.
- Studies do not seem to suggest that people who got the
vaccine have experienced a higher rate of cancer, but the virus, called
SV40, does have the potential to damage cells and turn them cancerous,
the Institute of Medicine panel said.
- When the injected polio vaccine was first developed,
it was grown on tissue taken from the kidneys of monkeys. In 1960, researchers
found that these tissues could be infected with SV40, a previously unknown
virus that causes a common and harmless infection in some monkeys.
- Scientists moved to take it out, and the polio vaccine
has been free of SV40 since 1963.
- Polio is a disease that kills or paralyzes. It once left
thousands of children living in "iron lungs," unable to breathe.
At its peak in the United States in 1952, polio caused more than 20,000
cases of paralysis.
- Thanks to the vaccine, polio was eliminated from the
Western Hemisphere by 1994. Work is underway to eradicate it from pockets
in parts of Africa and Asia.
- "Researchers estimate that 10 percent to 30 percent
of the polio vaccine given to adults and children in the United States
between 1955 and 1963 was contaminated with SV40, potentially exposing
between 10 million and 30 million Americans to the virus," the Institute
of Medicine, which put together the panel that wrote the report, said in
- "However, as with all viruses, not everyone who
comes into contact with SV40 will become infected," it added.
- The institute, an independent study group that reports
to Congress and the federal government on medical issues, said there is
no need to review polio vaccine policy as the vaccine has been free of
the virus for decades.
- At issue is whether people who claim to have developed
cancer because of the vaccine have a legitimate complaint. There is not
enough evidence to tell, the panel concluded.
- "The vast majority of population studies, which
carry the most weight in establishing causal relationships, have found
no increased rates of cancer in people who received the vaccine contaminated
with simian virus-40," it said in a statement.
- "However, a possible link cannot be completely ruled
out because of limitations in the available data and in the way the studies
- The group also noted that the virus does seem to be capable
of changing cells, perhaps starting the uncontrolled growth that is the
hallmark of cancer.
- "While there is a strong body of biological evidence
that SV40 is capable of causing cancer, it is not clear that exposure to
the virus through the tainted polio vaccine could cause certain cancers
suspected of being associated with SV40 -- mesothelioma, osteosarcoma,
ependymoma and non-Hodgkin's lymphoma," it added.
- Copyright © 2002 Reuters Limited. All rights reserved.
Republication or redistribution of Reuters content is expressly prohibited
without the prior written consent of Reuters. Reuters shall not be liable
for any errors or delays in the content, or for any actions taken in reliance