A large federal study concludes a mercury-based preservative used
in vaccinations given to children a decade or more ago does not
raise the risk of neurological problems.
However, the study did not examine autism — the developmental
disorder that some critics blame on vaccines. A separate study due
out in a year will report on that issue, said scientists at the
federal Centers for Disease Control and Prevention, who led the
latest analysis and published results in Thursday's New England
Journal of Medicine.
They found no clear connection between early exposure to the
preservative thimerosal and problems with brain function and
behavior in children age 7 to 10. The results are in line with past
research that found no connection between vaccines and neurological
problems or autism.
Thimerosal (pronounced thih-MEHR'-uh-sawl) has not been used in
childhood vaccines since 2001, although it is still in some flu
shots. The new findings apply to children immunized before then, or
exposed to the preservative through shots their mothers received
while pregnant. Thimerosal was put in vaccines to prevent
contamination from bacteria.
Some doctors say the CDC study should reassure parents worried
about the safety of vaccines.
"It's good news for families," said Dr. Michael Goldstein, vice
president of the American Academy of Neurology who works in private
practice in Salt Lake City. "There's no evidence that these
vaccines have caused injury."
The study involved 1,047 children who were exposed to varying
levels of thimerosal while in the womb or after birth in the 1990s.
The children belonged to four health maintenance organizations that
are part of a federal project to study the side effects of
vaccines. Their mercury exposure was determined through medical and
immunization records and interviews with parents.
Each child was tested for speech and language skills, motor
coordination and intelligence. Parents, teachers and trained
specialists also rated stuttering, attention span and tic disorders
such as head shaking, eye blinking and neck jerking. A total of 42
neurological problems were analyzed.
(Agencies via Xinhua News Agency September 28, 2007)
