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America's Vaccine Safety Watchdog |
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| Frequently
Asked
Questions |
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What evidence is there that it's appropriate to use the EPA's methyl-mercury guideline of 0.1mcg/kg/day in the VIC as the reference value for evaluating the levels of ethyl-mercury contained in Thimerosal? There are no specific standards for "safe" exposure
levels for ethyl-mercury for any population including infants.
The
Food and Drug Administration evaluated this issue in its report,
Thimerosal in Vaccines, and discussed the comparability of ethyl- and
methyl-mercury. This is their conclusion:
The various
mercury guidelines are based on epidemiological and
laboratory studies of methyl mercury, whereas thimerosal is a
derivative of ethyl mercury. Because they are different chemical
entities - ethyl- versus methylmercury - different toxicological
profiles are expected. There is, therefore, an uncertainty that arises
in applying the methylmercury-based guidelines to thimerosal. Lacking
definitive data on the comparative toxicities of ethyl- versus
methylmercury, FDA considered ethyl-
and methyl-mercury as
equivalent
in its risk evaluation. (http://www.fda.gov/
There are several standards for
methyl-mercury exposure. In 2000, the National Research
Council dealt with this issue and in it's report, The Toxicological
Effects of Methyl Mercury, it
stated, "on the basis of its analysis of the available data, the
committee finds that the value of the EPA’s
current RfD for MeHg (0.1
µg/kg per day) is scientifically justified for the protection of
public
health" (page 329).
(What is an RfD?)
This
is the rationale for using the EPA
methyl-mercury exposure guideline in
the VIC as the basis for comparing vaccine-based ethyl-mercury
exposures. We are aware of the differences between ethyl- and
methyl-mercury and the need for more science in this area. We are
also
aware that the EPA standard was developed for ingestion of
methyl-mercury contaminated fish in adults and may be too lax
for evaluating injection of ethyl-mercury in infants. You
may want
to visit the "Mercury
in
Vaccines" section of the website to learn more about these
issues.
Are "Thimerosal-free" vaccines really 100% free of all Thimerosal? I've heard that there could still be small (or trace) amounts of Thimerosal in the vaccine - and yet it can still be called "Thimerosal-free." There are potential areas of confusion about the difference between Thimerosal-trace and Thimerosal-free vaccine. Prior to launching the calculator we reviewed all of the product inserts on the FDA's website several times. Most of the manufacturer's stated exactly how much Thimerosal was included in the vaccine and if there was no Thimerosal - they stated what was used as a preservative in it's place and some stated very clearly that no Thimerosal was used in the manufacturing process. If the manufacturer stated that trace Thimerosal was present due to manufacturing (typically < 1.0 mcg per .5ml dose), that figure was used in the VIC. We are assuming that the information in the manufacturer's product inserts on the FDA's website is accurate. Limitations: What does the VIC not do? The VIC is currently designed for "vaccination planning" for a single day's office visit. It cannot account for past exposure nor for future exposure (as when parents are told to come back in a month for a second flu shot). If you print out and file the Vaccination Record, it will be easy to track exposure over time. Browser Issues 1. The Vaccination Record report isn't opening in my browser. It appears to be broken. What's the problem? If you are using Internet Explorer 6 or 7, this is a known bug that Microsoft has fixed. For details about the issue and how to fix it, click here. Fixing the problem requires that you "install the most current cumulative security update for Internet Explorer" or installing Internet Explorer 8. If you don't wish to do that, you might consider trying another browser, such as Firefox. |