Polio vaccine contaminated
2004-07-07 20:07
Paris - Hundreds of millions of people in Eastern Europe, Asia and Africa may have been injected with a Soviet polio vaccine which was contaminated by a monkey virus that has now been linked to cancer, New Scientist says.
Shoddy standards in Soviet vaccine plants meant that decontamination of the so-called simian virus 40 (SV40) was only 95% effective, it says.
This meant that for nearly 20 years after SV40 was supposed to have been screened out, the Soviet Union continued to ship potentially infected vaccines to its Eastern European allies and elsewhere.
"The vaccine was almost certainly used throughout the Soviet bloc and [was] probably exported to China, Japan and several countries in Africa," the British science weekly reports in next Saturday's issue.
"That means hundreds of millions could have been exposed to SV40 after 1963."
After the polio vaccine was invented in 1955, pharmaceutical labs used cells from rhesus monkeys to prepare doses in commercial quantities.
In 1960, SV40 was found in monkeys and soon after was detected in injected polio vaccines. In 1963, it was supposed to have been eliminated from all new vaccines worldwide.
The New Scientist report quotes a leading researcher on the SV40 problem, Michele Carbone of the Loyola University Medical Centre in Chicago, who found infectious SV40 virus in two out of three stored samples of live Soviet vaccines.
He found no SV40 virus in the third sample, but there was no infectious poliovirus either, which may indicate that the sample had degraded.
Carbone also tested the Soviet decontamination method, which used magnesium chloride in a bid to destroy SV40 in the vaccine.
He found it was only 95% effective, meaning that 5% of any virus may still have been lurking in Soviet polio vaccines.
It was only in 1981 that the danger was eliminated, when the Soviet Union switched to a vaccine seed free of SV40 that was provided by the World Health Organisation (WHO).
As to whether SV40 is dangerous, opinions are divided.
According to the US Centres for Disease Control (CDC) website, the virus has been found in certain types of cancer in humans - but, it says, there is no proof that the virus caused these cancers.
- AFP