| Saturday August 7, 2004 09:32 AM | |
LONDON (Reuters) - Babies will no longer be given a vaccine containing mercury, the Department of Health says, after pressure from parents fearing a possible link with autism.
Mercury had been contained within the whooping cough vaccine, given to babies when they are 8 weeks old.
A mercury-free jab will now be given to children as part of a new 5-in-1 vaccine for diphtheria, tetanus, whooping cough, hib and polio, Health Minister John Hutton said.
"Following advice from our expert committees we have decided that at the same time thiomersal, a mercury based preservative, will be removed from the new combined vaccine," Hutton said in a statement.
Research in the United States suggested that a mercury-based preservative used in some childhood vaccines was linked to autism-like damage in the brains of mice, the Daily Telegraph said.
However, the Department of Health has said there is no evidence of a link between mercury in vaccines and autism.
Doctors are also being told by the government to switch from the live polio vaccine, given by mouth, to a vaccine that can be combined with others in a single injection to avoid the rare cases of polio contamination.
Campaigners welcomed the removal of mercury but were worried about giving babies five vaccines at once.
"Giving five vaccines increases the risk of an adverse event as well as making it more difficult to find out which element is the cause if something goes wrong," Jacquie Fletcher, founder of the parent support group Jabs (Justice, Awareness and Basic Support) told the Telegraph.
The changes are expected to take place next month when sufficient stocks of the new five-in-one vaccine have been amassed.
Parents have already raised much concern about the triple jab for measles, mumps and rubella and its possible link with autism.
American researchers say that their study supports the findings of Andrew Wakefield, the discredited gastroenterologist who raised fears that the measles, mumps and rubella injection might be causing autism.
Uptake of the vaccine decreased sharply after Dr Wakefield suggested that MMR should be avoided in favour of single vaccinations. His research, published in The Lancet in 1998, detected traces of the measles virus in the guts of 12 children with autism.
The latest study, led by Arthur Krigsman, of New York University School of Medicine, involved 275 children. Serious intestinal inflammations were found in some of the autistic children and biopsies of gut tissue were performed on 82 of them. Of these, 70 are said to have shown evidence of the measles virus, which so far has been confirmed in 14 cases by more stringent DNA tests.
Steve Walker, assistant professor at Wake Forest University Medical Centre, North Carolina, who analysed the gut samples, said the work mirrored Dr Wakefield’s study. All the children involved were diagnosed with autism and had come to Dr Krigsman and Dr Walker seeking help for symptoms of serious digestive problems for which no explanation could be found.
The research, which is being presented at the International Meeting for Autism Research in Montreal this week, has yet to be published in a scientific journal and subjected to peer review.
Mainstream science has repeatedly examined the theory of a link between MMR and autism and found no evidence to back it. Supporters of the theory are accused of interpreting two biological occurrences as a causative relationship that does not exist.
Uptake of MMR, which was introduced into Britain in 1988, has improved in recent years, but remains as low as 70 per cent in the wake of ongoing questioning of its possible side-effects. The World Health Organisation recommends 95 per cent coverage, and the shortfall has been blamed for contributing to rising rates of measles and mumps in recent years.
A recent analysis of 31 MMR studies by the Cochrane Library, one of the most authoritative sources of evidence-based medicine, showed no credible grounds for claims of serious harm.
CHICAGO – A new study from Italy adds to a mountain of evidence that a mercury-based preservative once used in many vaccines doesn't hurt children, offering more reassurance to parents.
In the early 1990s, thousands of healthy Italian babies in a study of whooping cough vaccines got two different amounts of the preservative thimerosal (pronounced thih-MEHR'-uh-sawl) from all their routine shots.
Ten years later, 1,403 of those children took a battery of brain function tests. Researchers found small differences in only two of 24 measurements and those "might be attributable to chance," they wrote in the February issue of the journal Pediatrics, which was released Monday.
Only one case of autism was found, and that was in the group that got the lower level of thimerosal.
Autism is a complex disorder featuring repetitive behaviors and poor social interaction and communication skills. Scientists generally believe genetics plays a role in causing the disorder; a theory that thimerosal is to blame has been repeatedly discounted in scientific studies.
"Put together with the evidence of all the other studies, this tells us there is no reason to worry about the effect of thimerosal in vaccines," said the new study's lead author, Dr. Alberto Tozzi of Bambino Gesu Hospital in Rome.
The debate over thimerosal and autism has been much stronger in the United States than in Italy, Tozzi said. But the researchers recognized a chance to examine the issue by going back to the children who had taken part in the 1990s whooping cough research.
Randomization sets the new study apart. The random assignment of children rules out the chance that factors other than thimerosal, such as education or poverty, caused the results.
Thimerosal, used in some vaccines to prevent the growth of bacteria and fungus, hasn't been in U.S. childhood vaccines since 2001, except for certain flu shots. Italy and other European nations began removing it in 1999. U.S. health officials recommended the removal of thimerosal as a precaution and to reduce the overall exposure of children to mercury.
Safety regulations still require multi-dose vials of vaccines to contain some type of preservative to prevent the spread of infection from contaminated vials.
The study, funded by the U.S. Centers for Disease Control and Prevention, drew praise from outside experts.
"It's yet another well done, peer-reviewed research study that has demonstrated there is no risk of any neurodevelopmental outcomes associated with thimerosal in vaccines," said epidemiologist Jennifer Pinto-Martin of the University of Pennsylvania.
"This becomes the fourth study to look for subtle signs of mercury toxicity and show the answer was 'no,'" said Dr. Paul Offit, chief of infectious diseases at the Children's Hospital of Philadelphia, the author of a book on autism research and the co-inventor of a rotavirus vaccine.
Tozzi said comparing children with no exposure to thimerosal could have improved the study. "However, if thimerosal were a cause of harm, it is likely that this effect would increase with the administered dose," he said.
The children received either 62.5 micrograms or 137.5 micrograms of ethyl mercury from all their shots during their first year of life. Thimerosal breaks down as ethyl mercury in the body. Before the reduction of thimerosal in the United States, the maximum exposure for infants was 187.5 micrograms of ethyl mercury.
The researchers found the children in both groups scored, on average, in the normal range on 11 tests of memory, attention, motor skills and other brain functions.
Those 11 tests included 24 measured outcomes. Small, but statistical differences were found for only two of those areas, and only for girls. The girls with higher exposure scored worse on a finger-tapping test with their dominant hands, and on a vocabulary test in which they were asked to name common objects.
There was no difference in boys on those outcomes or others. Researchers also found no difference in tic disorders. And the one autism case found in the lower-intake group was likely a chance finding, Tozzi said.
___