Ever since the late Eighteenth-century English scientist Edward Jenner
created the first effective vaccine (against smallpox), scientists have
searched for more vaccines to inoculate patients against what they would later
understand to be viruses. Modern distribution and manufacture of vaccines
requires a reliable preservative to reduce the risk of microbial contamination of
them. Vaccines that are left to fester unpreserved would, in turn, infect with
diseases the very population they try
to protect in the first place. In the early 1930’s, pharmaceutical company Eli
Lilly, marketed a new preservative under the name
Merthiolate, which later became widely known as
Thimerosal after it supplanted other preservatives
as the best choice for vaccine preservation. Thimerosal, a compound made from mercury,
is an effective antimicrobial agent against a wide range of bacteria and fungi.
Thimerosal contains 49.6% mercury by weight (
Marques
2007). Despite obvious concerns with taking in doses of mercury, a deleterious
neurotoxin, the Centers for Disease Control and Prevention states that, “The
medical community supports the use of Thimerosal in influenza vaccines to
protect against potential bacterial contamination of multi-dose vials”
(CDC).
The CDC may indeed be correct in its support Thimerosal, considering it
has more than 70 years of history in use as a vaccine preservative. But, when
considering the toxicity of the mercury component that it contains, those who
want to ask more questions about its safety might not get simple answers.
Consider mercury’s toxicity to humans. Mercury (Hg) is the only metal that is
found in liquid form at room temperature. It also vaporizes easily at room
temperature, making it easily inhalable. Due to its lipid solubility, it can
easily enter the bloodstream through the alveoli and gets quickly picked up by
the red blood cells. When exposed to mercury in this manner, small amounts
persist in the body for years, and it can damage the central nervous system.
Mercury can also damage the brain, liver, cause attention problems, hearing and
sight difficulties (or total loss), loss of balance, slurred speech, and even cause
death. Symptoms of mercury poisoning are often mistaken for more common
illness, due to non-specificity of symptoms. Even more alarming is that the way
it acts in humans is “in many ways still a mystery” (
Lee, 2010).
In one particularly tragic instance in 1996, Karen E. Wetterhahn, a
professor of chemistry at Dartmouth College, and founding professor of that
institution’s Toxic Metals Research Program, died when exposed to only a few microliters
of a mercury compound. She exhibited the aforementioned symptoms, and spent the
last few months of her life thrashing about in an unconscious state in her
hospital room. It took five months after exposure for the symptoms to begin, and
died less than a year later, despite ongoing aggressive treatment (
a
tribute to Wetterhahn).
Just as worrisome, is the fact that through environmental pollution,
humans regularly receive exposure to mercury in their diets and environments. Coal
burning power plants, a primary source of pollution, release mercury into the
atmosphere, which in turn, helps the atmospherically suspended mercury to
eventually finds its way in the world’s bodies of water. The levels of mercury
in the oceans are creating a health risk to those who include fish in their
diets. On one hand, the government (FDA) recommends that fish replace fatty
meats at least twice per week in Americans’ diets to reduce the risk of heart
disease, and yet the same body warns of another threat, the potential to
accumulate high levels of mercury in the body through too much consumption of
fish. The United States Food and Drug Administration recommends only twelve
ounces of fish per week, and even fewer ounces, for some fish, such as shark,
tilefish, and some tunas, for pregnant women and children (
FDA).
When it comes to vaccines, their effectiveness is hardly in question. Refusing
a flu vaccine, for example, puts one at a greater peril of contracting disease
than from an allergic reaction resulting from the small amount of mercury compound
taken into the blood. The recent false connection between vaccines and autism
onto which the public latched its paranoia in recent years has only complicated
matters. “Today, in some parts of the United States, vaccination rates have
dropped so low that the incidence of certain childhood diseases is approaching
levels that existed before effective vaccines became available” (
Straub,
2006).
The question is, why take mercury at all, if given a choice? Although the
relationship between autism and mercury compounds (Thimerosal) used to preserve
vaccines has been debunked, the toxicity of mercury to humans is undisputed, and
thus shouldn’t Thimerosal be avoided, if possible? Evidently, not all medical
professionals agree that Thimerosal is worth the risk. Indeed, Thimerosal had
already been removed from many vaccines beginning in the 1980’s, especially from
those administered to infants. It has not, however, been removed in some
vaccines for adults, such as the annual flu vaccine. Single dose, non-preserved
vaccines are available, but not in quantities sufficient for the entire
population to receive a dose. Research on alternatives, such as Phenol-based
preservatives, is in progress. Early trials of vaccines with phenols for cutaneous
leishmaniasis, a parasitic skin disease, are proving promising (
Mayrink,
2006).
The solution would not be terribly complicated. Avoiding Thimerosal in
vaccines would require continued research into developing a wider array of
preservatives from which vaccine manufacturers could chose. It would be likely
for the public, assuming their awareness of mercury’s toxicity, to prefer
vaccines without it, and they could then opt to avoid an unnecessary risk for
themselves and their children. Secondly, since preservative-free vaccines (e.g.
flu vaccine) are already available, manufacturers could potentially increase
production of these doses, and in doing so, would make this a viable solution
for everyone.
Vaccine regimens should and will retain their important role in therapy
for public health. The safety of them far outweighs their risk, but risks do
remain unnecessarily present given the known toxicity of mercury. It is
obviously difficult to control the levels of mercury that the population is
exposed to from the environment. Perhaps in the future it will not be necessary
for anyone to accept the risk of additional, unnecessary mercury accumulation sourced
from vaccines.
