MERCURY, one of the most dangerous substances known to man, is being used in a series of infant vaccines - in spite of a warning from NHS advisers that its use as a cheap preservative "may be toxic" to babies aged under six months.
Thimerosal, a compound 50 per cent composed of ethyl mercury, which is banned in the United States amid fears of its links to autism, is being used in the DTwP vaccines given to infants aged eight weeks.
A report from NHS scientists has indicated that thimerosal is not only dangerous to infants, but also to the unborn child if contained in products used by pregnant women.
The UK Medicines Information (UKMI) service, run under the NHS banner to provide advice to doctors, has compiled a report naming the 13 UK vaccines which contain thimerosal - referred to as "thiomersal" by some scientists.
The list includes four out of the seven flu vaccines issued this year by the government, a pneumonia vaccine and four of the 11 child vaccines. The main source is the triple DTwP jab, for whole-cell diphtheria, tetanus and pertussis.
There is no mercury in vaccines for MMR, polio, meningitis C or the DTaP injection, which also protects against diphtheria and tetanus. But UK infants are always given the DTwP vaccine, which does contain mercury.
"The very low thiomersal concentrations present in the pharmacological and biological products are relatively non-toxic in adults," the UKMI report says. "But it may be toxic in utero [in the foetus] and during the first six months of life."
It is the first time any UK health official has admitted to the danger posed by mercury in vaccines.
Pressure groups described the UKMI advice as a "bombshell" which should "make Britain wake up to what the Americans have known for years" and force ministers to take mercury out of all medicine.
Action Against Autism, a pressure group, said this tallied with the boom in autism since vaccination ages were lowered in 1990.
"If the Department of Health is aware that thimerosal is unsafe for childhood vaccines, than we may be looking a criminal medical negligence on a massive scale," said Bill Welsh, the group’s chairman.
The Department of Health last night confirmed to The Scotsman that the UK vaccination schedule will have exposed infants to thimerosal, and therefore mercury, three times by the age of 17 weeks.
"The level of thiomersal present is 50 micrograms per injection," a spokesman said. "UK childhood exposure to thiomersal is via DTP-containing vaccine only and, as such, up to four months of age-cumulative exposure to thiomersal is 150 micrograms from three injections."
Although it did not refute that this substance is toxic, it said the UK Committee on Safety of Medicines "has advised that there is no evidence of harm caused by doses of thiomersal in vaccines, except for hypersensitivity reactions".
It is hypersensitive reactions to thiomersal, however, which are now being linked to autism by research. The UKMI advice says as many as 18 per cent of children - almost one in five - can experience side-effects.
It added that a memo warning about the toxic risk in thiomersal was provided by the Wessex Drug and Medicines Information Centre in Southampton University Hospitals Trust, dated October 2002.
The Department of Health said it was "independent advice from independent doctors" and that it is not necessarily endorsed by ministers.
Thimerosal has been used in vaccines since 1939. The first case of autism was diagnosed four years after - a condition never before recorded in medical science.
The US Institute of Medicine has warned that thiomersal has a "biologically plausible" link to autism, an admission which has fuelled 30 billion class action in the US against Eli Lilly, the main thiomersal producer.
The Scottish Parliament has the power to ban mercury in vaccines. In spite of pressure from the SNP and the Tories, ministers have decided to stay within the UK vaccination programme.