U.S. Public Health Service
American Academy of Pediatrics
July 10, 1999
Infant Vaccines Containing
Thimerosal May Exceed Federal Thresholds for Mercury Levels
DETROIT - (www.safetyalerts.com) The American Academy of Pediatrics
(AAP) and the U.S. Public Health Service (PHS) have released a joint statement on the
potential for exceeding a federal acceptable threshold for cumulative levels of mercury in
infants receiving Thimerosalcontaining vaccines in the first six months of
life. Thimerosal is a mercury-containing preservative present in many but not all
Excessive levels of mercury may cause adverse
neurodevelopmental effects; however, there is no evidence that such adverse effects
actually occur among children exposed to thimerosol in vaccines. Because of the
theoretical risk of adverse effects from mercury accumulation, changes are being
instituted in vaccine manufacturing processes to eliminate any exposure to mercury.
In order to minimize exposure to thimerosal at
this time, changes based on the flexibility in the hepatitis B vaccination schedule should
be considered for infants born to hepatitis B surface antigen (HbsAg)negative
mothers. Such infants should have the first dose of hepatitis B vaccine postponed from
birth until 2 to 6 months of age. Pre-term infants born to hepatitis B surface
antigennegative mothers should likewise have the first dose of hepatitis B vaccine
delayed until they reach term gestational age and a weight of at least 2.5 kg. Because of
the substantial risk of disease, there is no change in the recommendations for infants of
HbsAg-positive mothers or of mothers whose status is not known. Also, in populations
where HbsAg screening of pregnant women is not routinely performed, vaccination of all
infants at birth should be maintained, as is currently recommended. No other changes
in currently recommended practices are indicated.
Both the PHS and AAP continue to recommend all
children be immunized according to the current child immunization schedule.
The recognition that some children could be
exposed to a cumulative level of mercury over the first six months of life that exceeds
one of the federal guidelines on methyl mercury now requires a weighing of two different
types of risks when vaccinating infants. On the one hand, there is the known serious risk
of diseases and deaths caused by failure to immunize our infants against
vaccine-preventable infectious diseases; on the other, there is the unknown and probably
much smaller risk, if any, of neurodevelopmental effects posed by exposure to thimerosal.
The large risks of not vaccinating children far outweigh the unknown and probably much
smaller risk, if any, of cumulative exposure to thimerosal-containing vaccines over the
first six months of life.
Nevertheless, because any potential risk is of
concern, the Public Health Service, the American Academy of Pediatrics, and vaccine
manufacturers agree that thimerosal-containing vaccines should be removed as soon as
For your information we have attached a Table listing the thimerosol status of available vaccine products
as well as a page of "Frequently Asked Questions" on
The US Public Health Service and the American
Academy of Pediatrics are working collaboratively to assure that the replacement of
thimerosal-containing vaccines takes place as expeditiously as possible while at the same
time ensuring that our high vaccination coverage levels and their associated low disease
levels throughout our entire childhood population are maintained.
The key actions being taken are:
1. A formal request to manufacturers for a clear
commitment and a plan to eliminate or reduce as expeditiously as possible the mercury
content of their vaccines.
2. A review of pertinent data in a public
3. Expedited FDA review of manufacturers'
supplements to their product license applications to eliminate or reduce the mercury
content of a vaccine.
4. Provide information to clinicians and public
health professionals to enable them to communicate effectively with parents and consumer
5. Monitoring immunization practices, future
immunization coverage, and vaccine-preventable disease levels.
6. Studies to better understand the risks and
benefits of this safety assessment.
All information is general in nature and is
not intended to be used as a substitute for appropriate professional advice, contact your
physician or healthcare provider for more information.
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