Is the influenza vaccine safe during pregnancy?
By Medical Advisory Board
The influenza vaccine appears to be safe for use
Various studies to date have found no increase in the rate
of major birth defects in the infants of women who received influenza vaccine during any trimester
of their pregnancy [10-12,13,21 ]. "During 2000--2003, an estimated 2 million pregnant
women were vaccinated, and only 20 adverse events among women who received
trivalent inactivated influenza vaccine were reported to the Vaccine Adverse Event Reporting System (VAERS) during this time,
including nine injection-site reactions and eight systemic reactions (e.g.,
fever, headache, and myalgias).
Pregnant women are at increased risk
for influenza-associated illness and death [1-6]. Women in their third
trimester of pregnancy appear to be especially likely to be hospitalized for
an acute cardiopulmonary illness during influenza season  Influenza
vaccines offer an effective means for reducing cases of influenza,
especially when the composition of the vaccine matches the circulating
type of influenza. [8,9,22,23].
In addition, maternal influenza immunization has
also been shown to
significantly reduce the rate of influenza in the infants of
vaccinated mothers and could be used to protect vulnerable
newborns against strains of flu such as H1N1 .
Presently the Advisory Committee on Immunization Practices (ACIP) recommends
vaccination of all women who are pregnant or will be pregnant during
influenza season with inactivated influenza vaccine .
Are the preservatives in influenza vaccines safe?
Concerns regarding the presence of the mercury-based
preservative thimerosol found in the multidose influenza vaccine appear to be unfounded. The amount
of mercury in each
dose of influenza vaccine is about the same amount of mercury found in nine
ounces of canned tuna, and is in a form that appears to be rapidly
eliminated from the body.
There is no convincing evidence of harm caused by the small amount of thimerosal in vaccines, except for minor effects such as swelling and redness at the injection site due to
sensitivity to thimerosal. Currently, the U.S. Environmental Protection Agency uses a reference dose of 0.1 µg/kg body
weight/day as a methylmercury exposure without recognized adverse effects .
Each dose of inactivated flu vaccine contains 25 micrograms of mercury . 25 micrograms of mercury is far below the U.S. EPA
reference dose for the average 155 pound (70 kg) woman, and is about
the same amount of mercury found in nine ounces of canned tuna . I addition
the mercury in thimersol is in the form of
which appears to be eliminated from blood rapidly via the stools after
administration of thiomersal in vaccines. Interpretation
Administration of vaccines containing thiomersal does not seem to raise
blood concentrations of mercury above safe values in infants. Ethylmercury
seems to be eliminated from blood rapidly via the stools after parenteral
administration of thiomersal in vaccines .
Nonetheless, certain states have enacted legislation that limits the amount of
mercury in vaccines administered to pregnant women and very young children. (19,
Are there adjuvants in influenza vaccines?
No. Neither the influenza A (H1N1) vaccine
nor the seasonal influenza vaccines contain adjuvants.
Adjuvants are compounds added to vaccines that stimulate the body's immune
system to react to some of the viral parts that may not cause a sufficient
response on their own. They could also be used to allow a smaller dose of
the virus to be given in order to stretch the amount of a vaccine
that is in short supply [26,27].
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26.MMWR .August 28, 2009 / 58(RR10);1-8. Use of Influenza A (H1N1) 2009 Monovalent
Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009