Pre-1963 polio vaccines may be killing hundreds through cancer

Pre-1963 polio vaccines may be killing hundreds through cancer

By Robert Matthews Science Correspondent

THE mass vaccination campaigns of the Fifties and Sixties may be causing hundreds of deaths a year because of a cancer-causing virus which contaminated the first polio vaccine, according to scientists.

Known as SV40, the virus came from dead monkeys whose kidney cells were used to culture the first Salk vaccines. Doctors estimate that the virus was injected into tens of millions during mass vaccination campaigns before being detected and screened out in 1963. Those born between 1941 and 1961 are thought to be most at risk of having been infected.

Now a new study of the effects of SV40 points to disturbing evidence that the monkey virus causes a number of human cancers. It concludes that there is "compelling" evidence linking SV40 to mesothelioma, a once-rare type of lung cancer whose prevalence is rapidly increasing.

Dr Janet Butel of the Baylor College of Medicine, Texas, and the lead author of the study, told The Telegraph: "I feel strongly that research is warranted to determine how common human infections by SV40 may be, and what factors might predispose individuals to SV40-related tumours." Her study, published in the Journal of the National Cancer Institute, also suggested that the monkey virus may be passing from those given the contaminated vaccine to their children, spreading the cancer risk still further.

Blood samples analysed by Dr Butel and her colleagues point to the steady spread of the cancer-causing virus in the human population, with 10 per cent of those never exposed directly to the contaminated vaccine testing positive for SV40. Dr Butel said: "I believe SV40 is present in the human population today and is being spread among individuals by an unknown route."

The Telegraph has learnt that scientists in Britain have joined an international effort to confirm the findings. According to Prof Gordon McVie, the director general of the Cancer Research Campaign, researchers have so far uncovered evidence linking SV40 to a number of cancers, including brain tumours and bone cancer. He said: "I've a feeling that the virus might be implicated in more, such as non-Hodgkin's lymphoma and prostate cancer."

The study is also likely to prompt a radical rethink by doctors of what happened 40 years ago, during the early days of polio vaccination. Until now, SV40 was regarded as harmless, with no evidence of long-term health effects emerging in follow-up studies of those vaccinated.

Now it appears that these studies may not have been conducted over a long enough period. New highly sensitive laboratory tests have disclosed the presence of SV40 in many different types of human tumour.

The most startling results centre on mesothelioma, until recently linked primarily to exposure to asbestos. Studies have found that around 70 per cent of mesothelioma cases test positive for the SV40 virus. Over the past 30 years, the number of mesothelioma cases has risen 10-fold, to about 1,000 a year, and is predicted to reach 4,000 early next century.

Until now, the increase was blamed on the asbestos industry. But the new findings are leading scientists to suspect that SV40 may account for a substantial number of mesotheliomas. Dr Butel said: "The consistent association of SV40 with that tumour is compelling."

Some scientists remain sceptical of the link, however. Robin Weiss, a professor of viral oncology at University College, London, said that SV40 is widely used in laboratories and could easily contaminate tumour samples, fooling the ultra-sensitive tests used to detect the virus. Prof Weiss said: "Many of the positive results are probably false positives. We've looked at mesothelioma and did find it in some cases, but then we got bogged down in whether they were due to contamination or not."

However, Dr Bharat Jasani, a leading expert on SV40 and mesotheliomas at the University of Wales College of Medicine, Cardiff, said that new reliability tests rule out contamination as a possible explanation. He said: "There is absolutely no question of laboratory contamination being to blame. That part of the story is now over. The time has come where we have to take things more seriously."

Dr Jasani said he had little doubt that the mass polio vaccination campaigns were to blame for SV40 entering the human population. He said, however, that this could bring new hope to hundreds of cancer patients, as it suggested that many might be treated by a vaccine that attacked SV40. He said: "We could think about saving more than 2,000 lives a year from mesothelioma - and that is good news."

A spokesman for the Department of Health said last night that it was aware that SV40 had contaminated early polio vaccines but insisted that there is no evidence that the virus caused tumours. She said: "It is also important to stress that the vaccine currently used is rigorously checked for safety and efficacy and is free of SV40."