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Vaccine Safety
June 24, 2005
La Marque
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A recent
news report has questioned the safety of vaccines
containing the preservative Thimersol.
The Texas Department of State Health Services (DSHS) has issued a
statement regarding the safety of vaccines containing
Thimersol. The statement below also contains links to
additional information on the subject.
June 22, 2005
Thimerosal is a preservative that was a component of
some vaccines. It was used to prevent microbial
contamination of multi-dose vials of vaccines, dating back
to the 1930’s. In 1999, the U.S. Public Health Service
called for the removal of thimerosal from recommended
childhood vaccines as a precautionary measure since it
contains ethylmercury (50% by weight). Little is known
about ethylmercury. Its properties are different from
methylmercury, the more common form of organic mercury
that, in high doses, can adversely affect the nervous
system. Other than local injection site reactions such as
redness or swelling, no known harmful health effects can be
attributed to thimerosal levels in vaccines. Vaccine
manufacturers have either removed thimerosal entirely or
reduced it to only trace amounts in the recommended
childhood vaccines. Since methylmercury, the type of
mercury commonly found in the environment, can cause
neurodevelopmental delays in infants exposed to high
levels, some hypothesized thimerosal could cause
neurodevelopmental disorders such as autism. However, high
doses of methylmercury have not been linked to autism.
Autism is a complex and often severe neurological disorder
with a broad range of characteristics, most notably
developmental delays and language, communication, and
social deficits.
The Institute of Medicine (IOM) recently published a
report: Immunization Safety Review 2004: Vaccines and
Autism. The review concluded that thimerosal-containing
vaccines were not associated with autism, and reaffirmed
the lack of association between measles-mumps-rubella (MMR)
vaccine and autism, which was concluded in an earlier IOM
report. A 2001 IOM report on thimerosal-containing
vaccines and neurodevelopmental disorders concluded that
there was not enough evidence for an association between
thimerosal-containing vaccines and autism and other
disorders. Population based research studies published
since 2001 have not revealed an association between
thimerosal-containing vaccines and autism in children. In
addition, a review published in Pediatrics (Parker SK, et
al. Pediatrics 2004 Sep; 114(3): 793-804) concluded that
the body of scientific research does not support a link
between thimerosal and autism.
Links to
additional information:
The Texas
Department of State Health Services Immunization Branch
website provides information on vaccine safety and numerous
links to additional resources. This information may be
accessed at:
http://www.tdh.state.tx.us/immunize/vac_safety.htm.
The Immunization Branch may also be contacted by calling
(800) 252-9152.
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