Vaccine preservative is not the cause of autism, say US officials
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《英国医生杂志》
Thiomersal, a mercury containing preservative used in children抯 vaccines known in the US as Thimerosal, is not the cause of autism, said top officials from key US government agencies at a joint news conference on 19 July.
The announcement, held one day before a rally sponsored by 11 autism groups in Washington, DC, caused a fierce reaction among parents?groups and several politicians, who criticised the government抯 claims as politically motivated and aimed, in part, at deterring product liability suits against makers of the vaccines.
The conference was held jointly by the Centers for Disease Control and Prevention (CDC), the National Institute of Child Health Development, and the Food and Drug Administration. Julie Gerberding, director of the CDC, said the briefing was held because of concerns that unwarranted fear of vaccination could lead to the re-emergence of diseases such as rubella. She said, "Rubella is a cause of autism, and during the most recent epidemic in the 1960s 7% of children with congenital rubella syndrome developed autism. Just this year we were dealing with a measles outbreak in the Midwest among people who were under-immunised for measles virus."
Dr Gerberding was joined by other officials who repeatedly emphasised that on the basis of many studies involving "thousands of children . . . the preponderance of evidence consistently does not reveal an association between thimerosal and autism."
Thiomersal, widely used in childhood vaccines in the United States during the 1990s, is now either not used or present in only trace amounts in childhood vaccines. However, flu vaccines still contain thiomersal, and new guidelines recommend several early childhood flu jabs. The removal of thiomersal came after a 2001 recommendation by the Institute of Medicine when it concluded that scientific evidence on the relationship between thiomersal and autism was inconclusive. Government officials cited a 2004 report by the institute that asserts that the "overwhelming evidence from several well-designed studies indicates that childhood vaccines are not associated with autism."
Congressman Dave Weldon (Republican, Florida), a practising physician before his election to Congress, criticised the government, saying that four of the five key studies cited were from Denmark, Sweden, and the United Kingdom, "where children received only one third to one half the amount of mercury as children in the US." Also, Dr Weldon said that the lead author of the only US study (Pediatrics 2003;112:1039-48) had concluded of his own study that "the bottom line is and has always been the same: an association between thimerosal and neurological outcomes could neither be confirmed nor refuted, and therefore, more study is required."
However, responding to the charge that researchers are denied full access to raw data from the publicly funded study published in Pediatrics, a CDC spokesperson said that data "are owned by private entities, managed care organisations," and that external researchers who want to analyse the database can obtain "limited access" to "analytic" and "final datasets" by following an application protocol and paying relevant fees.
Dr Weldon said he was not against vaccination and that his own 6 year old son has had all his vaccine jabs. He said portraying people who challenge the safety of thiomersal as anti-vaccination is an attempt to "vilify" people "who ask if our vaccines could be made safer." Dr Weldon is sponsoring a bill, the Mercury Free Vaccines Act, that would ban thiomersal from all vaccines.
In a scathing attack, Robert Kennedy Jr, senior attorney for the Natural Resources Defense Council, said the news conference was an attempt to shield vaccine companies from responsibility for the neurological effects of vaccines that contain thiomersal. A number of observers cite a recent article by Mr Kennedy as responsible, in some measure, for triggering the government news conference. In the article, published simultaneously by the online news magazine Salon (www.salon.com/news/feature/2005/06/16/thimerosal/index.html) and Rolling Stone, Mr Kennedy charged that the CDC and FDA have bought up the tainted vaccines "for export to developing counties" and that the government has concealed documents about the risks of thiomersal.
A CDC spokesperson denied this allegation, stating: "There has never been a programme at CDC to send thimerosal containing vaccines to developing countries."(Jeanne Lenzer)
The announcement, held one day before a rally sponsored by 11 autism groups in Washington, DC, caused a fierce reaction among parents?groups and several politicians, who criticised the government抯 claims as politically motivated and aimed, in part, at deterring product liability suits against makers of the vaccines.
The conference was held jointly by the Centers for Disease Control and Prevention (CDC), the National Institute of Child Health Development, and the Food and Drug Administration. Julie Gerberding, director of the CDC, said the briefing was held because of concerns that unwarranted fear of vaccination could lead to the re-emergence of diseases such as rubella. She said, "Rubella is a cause of autism, and during the most recent epidemic in the 1960s 7% of children with congenital rubella syndrome developed autism. Just this year we were dealing with a measles outbreak in the Midwest among people who were under-immunised for measles virus."
Dr Gerberding was joined by other officials who repeatedly emphasised that on the basis of many studies involving "thousands of children . . . the preponderance of evidence consistently does not reveal an association between thimerosal and autism."
Thiomersal, widely used in childhood vaccines in the United States during the 1990s, is now either not used or present in only trace amounts in childhood vaccines. However, flu vaccines still contain thiomersal, and new guidelines recommend several early childhood flu jabs. The removal of thiomersal came after a 2001 recommendation by the Institute of Medicine when it concluded that scientific evidence on the relationship between thiomersal and autism was inconclusive. Government officials cited a 2004 report by the institute that asserts that the "overwhelming evidence from several well-designed studies indicates that childhood vaccines are not associated with autism."
Congressman Dave Weldon (Republican, Florida), a practising physician before his election to Congress, criticised the government, saying that four of the five key studies cited were from Denmark, Sweden, and the United Kingdom, "where children received only one third to one half the amount of mercury as children in the US." Also, Dr Weldon said that the lead author of the only US study (Pediatrics 2003;112:1039-48) had concluded of his own study that "the bottom line is and has always been the same: an association between thimerosal and neurological outcomes could neither be confirmed nor refuted, and therefore, more study is required."
However, responding to the charge that researchers are denied full access to raw data from the publicly funded study published in Pediatrics, a CDC spokesperson said that data "are owned by private entities, managed care organisations," and that external researchers who want to analyse the database can obtain "limited access" to "analytic" and "final datasets" by following an application protocol and paying relevant fees.
Dr Weldon said he was not against vaccination and that his own 6 year old son has had all his vaccine jabs. He said portraying people who challenge the safety of thiomersal as anti-vaccination is an attempt to "vilify" people "who ask if our vaccines could be made safer." Dr Weldon is sponsoring a bill, the Mercury Free Vaccines Act, that would ban thiomersal from all vaccines.
In a scathing attack, Robert Kennedy Jr, senior attorney for the Natural Resources Defense Council, said the news conference was an attempt to shield vaccine companies from responsibility for the neurological effects of vaccines that contain thiomersal. A number of observers cite a recent article by Mr Kennedy as responsible, in some measure, for triggering the government news conference. In the article, published simultaneously by the online news magazine Salon (www.salon.com/news/feature/2005/06/16/thimerosal/index.html) and Rolling Stone, Mr Kennedy charged that the CDC and FDA have bought up the tainted vaccines "for export to developing counties" and that the government has concealed documents about the risks of thiomersal.
A CDC spokesperson denied this allegation, stating: "There has never been a programme at CDC to send thimerosal containing vaccines to developing countries."(Jeanne Lenzer)