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<General Questions and Answers on Thimerosal>
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Issue No. 003/09 |
20
November2009
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Main Topic:
H1N1 FLU
(SWINEFLU)
VACCINE
SAFETY
General
Questions and Answers on Thimerosal
September 14,
2009, 11:00 PM ET
What is thimerosal?
Thimerosal is a mercury-based preservative that has been used for decades
in the United States in multi-dose vials (vials containing more than one
dose) of some vaccines to prevent the growth of microorganisms, such as
bacteria and fungi, which may contaminate them.
What are preservatives
and why are they used in vaccines?
In vaccines, preservatives are used to prevent the growth of bacteria
and fungi in the event that they get into the vaccine. This may occur
when a syringe needle enters a vial as a vaccine is being prepared for
administration. Contamination by germs in a vaccine could cause serious
illness or death. In some vaccines, preservatives are added during the
manufacturing process to prevent microbial growth.
Will the 2009
H1N1 influenza vaccine contain thimerosal?
The 2009 H1N1 influenza vaccines that FDA is licensing (approving) will
be manufactured in several formulations. Some will come in multi-dose
vials and will contain thimerosal as a preservative. Multi-dose vials
of seasonal influenza vaccine also contain thimerosal to prevent potential
contamination after the vial is opened.
Some vaccine
manufacturers will be producing 2009 H1N1 influenza vaccine in single-dose
units, which will not require the use of thimerosal as a preservative.
In addition, the live-attenuated version of the vaccine, which is administered
intranasally (through the nose), is produced in single-units and will
not contain thimerosal.
I have concerns
about the use of thimerosal. Is thimerosal still being used?
People have a right to expect the vaccines they receive are safe and effective.
CDC and FDA also hold vaccines to the highest standards of safety. That
is why CDC and FDA continually evaluate new scientific information about
the safety of vaccines. Since 2001, no new vaccine licensed by FDA for
use in children has contained thimerosal as a preservative, and all vaccines
routinely recommended by CDC for children under six years of age have
been thimerosal-free, or contain only trace amounts, except for multi-dose
formulations of influenza vaccine. This was done as a precautionary step
and not because there was evidence confirming that thimerosal-containing
vaccines were causing health problems. The most recent and rigorous scientific
research does not support the hypothesis that thimerosal-containing vaccines
are harmful.
Thimerosal is
an important preservative that protects vaccines against potential microbial
contamination, which may occur in opened multi-dose vials of vaccine.
Such contamination could cause serious illness or death. Since seasonal
influenza vaccine is produced in large quantities for annual immunization
campaigns, some of the vaccine is produced in multi-dose vials, and contains
thimerosal to safeguard against possible contamination of the vial once
it is opened.
Three leading
federal agencies (CDC, FDA, and NIH) have reviewed the published research
on thimerosal and found it to be a safe product to use in vaccines. Three
independent organizations [The National Academy of Sciences' Institute
of Medicine, Advisory Committee on Immunization Practices (ACIP), and
the American Academy of Pediatrics (AAP)] reviewed the published research
and also found thimerosal to be a safe product to use in vaccines. The
scientific community supports the use of thimerosal in influenza vaccines.
Is thimerosal
safe when used as a preservative in vaccines?
CDC places a high priority on vaccine safety, surveillance, and research.
CDC is aware that the presence of the preservative thimerosal in vaccines
and suggestions of a relationship to autism has raised concerns. These
concerns make the decisions surrounding vaccinations confusing and difficult
for some people, especially parents. Numerous studies have found no association
between thimerosal exposure and autism. Since 2001, no new vaccine licensed
by FDA for use in children has contained thimerosal as a preservative
and all vaccines routinely recommended by CDC for children under six years
of age have been thimerosal-free, or contain only trace amounts, except
for some formulations of influenza vaccine. Unfortunately, we have not
seen reductions in the numbers of children identified with autism indicating
that the cause of autism is not related to a single exposure such as thimerosal.
The federal government
is committed to assuring the safety of vaccines. This is achieved by FDA
oversight of rigorous pre-licensure trials and post-licensure monitoring
by CDC and FDA. This commitment not only stems from our scientific and
medical dedication, it is also personal - for most of us who work at CDC
are also parents and grandparents. We too, place tremendous value on the
health and safety of children.
Links to non-federal
organizations are provided solely as a service to our users. These links
do not constitute an endorsement of these organizations or their programs
by CDC or the federal government, and none should be inferred. CDC is
not responsible for the content of the individual organization Web pages
found at these links.
| IOMS
Newsletter - 20 November 2009 |
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Issue
No. 003/09
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