A memo from Merck & Co. shows that, nearly a decade
before the first public disclosure, senior executives
were concerned that infants were getting an elevated
dose of mercury in vaccinations containing a widely
used sterilizing agent.
The March 1991 memo said that 6-month-old children who
received their shots on schedule would get a mercury
dose up to 87 times higher than guidelines for the maximum
daily consumption of mercury from fish.
"When viewed in this way, the mercury load appears rather
large," said the memo from Dr. Maurice R. Hilleman,
an internationally renowned vaccinologist. It was written
to the president of Merck's vaccine division.
The memo was prepared at a time when U.S. health authorities
were aggressively expanding their immunization schedule
by adding five new shots for children in their first
six months. Many of these shots, as well as some previously
included on the vaccine schedule, contained thimerosal,
an antibacterial compound that is nearly 50% ethyl mercury,
Federal health officials disclosed for the first time
in 1999 that many infants were being exposed to mercury
above health guidelines through routine vaccinations.
The announcement followed a review by the U.S. Food
and Drug Administration that was described at the time
as a first effort to assess the cumulative mercury dose.
But the Merck memo shows that at least one major manufacturer
was aware of the concern much earlier.
"The key issue is whether thimerosal, in the amount
given with the vaccine, does or does not constitute
a safety hazard," the memo said. "However, perception
of hazard may be equally important."
Merck officials would not discuss the contents of the
memo, citing pending litigation.
Separately, the drug giant is trying to fend off a legal
onslaught over Vioxx, the popular painkiller it introduced
in 1999. The company, based in Whitehouse Station, N.J.,
faces hundreds of lawsuits claiming that the drug caused
heart problems and that Merck concealed the risks. Merck,
which in September pulled Vioxx off the market, has
denied the allegations.
The legacy of thimerosal, meanwhile, also is causing
problems for Merck and other drug companies.
More than 4,200 claims have been filed in a special
federal tribunal, the Vaccine Injury Compensation Program,
by parents asserting that their children suffered autism
or other neurodevelopmental disorders from mercury in
vaccines. A handful of similar claims are awaiting trial
in civil courts. The plaintiffs cite various scientific
studies that they say prove the dangers of thimerosal,
including at the levels found in vaccines.
Thimerosal has been largely removed from pediatric vaccines
in recent years in what health officials have described
as a precautionary measure. (This has been accomplished
as drug makers have voluntarily switched from multi-dose
vials of vaccine, which require a chemical preservative
like thimerosal, to single-dose containers.)
In September, Gov. Arnold Schwarzenegger signed legislation
prohibiting vaccines with more than trace amounts of
thimerosal from being given to babies and pregnant women.
Iowa has a similar ban.
For their part, Merck and other vaccine makers, along
with many government health officials and scientists,
say there is no credible evidence of harm from the amounts
of mercury once widely present in kids' shots. They
cite a report in May by a committee of the national
Institute of Medicine concluding that the evidence "favors
rejection of a causal relationship" between vaccines
The seven-page Merck memo was provided to the Los Angeles
Times by James A. Moody, a Washington lawyer who works
with parent groups on vaccine safety issues. He said
he obtained it from a whistle-blower whom he would not
The memo provides the "first hard evidence that the
companies knew — or at least Merck knew —
that the children were getting significantly more mercury"
than the generally accepted dose, the lawyer said.
He also provided a copy to attorneys for Vera Easter,
a Texas woman who blames thimerosal for the condition
of her 7-year-old son, Jordan, who is autistic and mentally
retarded. The Easter lawsuit is pending in U.S. District
Court for the Eastern District of Texas. The defendants
include Merck; rival vaccine makers GlaxoSmithKline,
Aventis Pasteur Inc. and Wyeth; and thimerosal developer
Eli Lilly & Co.
Easter's lawyer, Andy Waters, described the memo as
"incredibly damning and incredibly significant." After
receiving it in the fall, he confronted Merck lawyers
about why he hadn't seen it earlier.
In a letter to Waters in October, Merck attorneys said
they had in fact made available 32 boxes of records,
but that the copying service hired by the plaintiffs
for some reason had failed to copy several of the boxes
— including the one with the Hilleman memo.
"The memo," said company spokeswoman Mary Elizabeth
Blake, "was produced voluntarily by Merck in the ordinary
course of discovery proceedings."
Hilleman is a former senior vice president of Merck
who developed numerous vaccines for the company. A 1999
profile in the Philadelphia Inquirer said that "it is
no exaggeration to assert, as many scientists do, that
Maurice Hilleman has saved more lives than any other
Hilleman, 85, currently director of the Merck Institute
for Vaccinology, had officially retired and was a consultant
to Merck when he wrote the '91 memo. He declined to
The memo was sent to Dr. Gordon Douglas, then head of
Merck's vaccine division and now a consultant for the
Vaccine Research Center at the National Institutes of
Health. Douglas also declined to comment.
The memo stated that regulators in several countries
had raised concerns about thimerosal, including in Sweden,
where the chemical was being removed from vaccines.
"The public awareness has been raised by the sequential
wave of experiences in Sweden including mercury exposure
from additives, fish, contaminated air, bird deaths
from eating mercury-treated seed grains, dental amalgam
leakage, mercury allergy, etc.," the memo said.
It noted that Sweden had set a daily maximum allowance
of mercury from fish of 30 micrograms for a 160-pound
adult, roughly the same guideline used by the FDA. Adjusting
for the body weight of infants, Hilleman calculated
that babies who received their shots on schedule could
get 87 times the mercury allowance.
The Swedish and FDA guidelines work out to about four-tenths
of a microgram of mercury per kilogram of body weight.
A stricter standard of one-tenth of a microgram per
kilogram has been adopted by the Environmental Protection
Agency and endorsed by the National Research Council.
These standards are based on methyl mercury, the type
found in fish and airborne emissions from power plants.
Though toxic, the ethyl mercury in thimerosal may be
less hazardous than methyl mercury, some scientists
say, because it is more quickly purged from the body.
"It appears essentially impossible, based on current
information, to ascertain whether thimerosal in vaccines
constitutes or does not constitute a significant addition
to the normal daily input of mercury from diverse sources,"
the memo said.
"It is reasonable to conclude" that it should be eliminated
where possible, he said, "especially where use in infants
and young children is anticipated."
In the U.S., however, thimerosal continued to be added
throughout the '90s to a number of widely used pediatric
vaccines for hepatitis B, bacterial meningitis, diphtheria,
whooping cough and tetanus.
It was added to multi-dose vials of vaccine to prevent
contamination from repeated insertion of needles to
extract the medicine. It was not needed in single-dose
vials, but most doctors and clinics preferred to order
vaccine in multi-dose containers because of the lower
cost and easier storage.
The Hilleman memo said that unlike regulators in Sweden
and some other countries, "the U.S. Food and Drug Administration
does not have this concern for thimerosal."
A turning point came in 1997 when Congress passed a
bill ordering an FDA review of mercury ingredients in
food and drugs.
Completed in 1999, the review revealed the high level
of mercury exposure from pediatric vaccines and raised
a furor. In e-mails later released at a congressional
hearing, an FDA official said health authorities could
be criticized for "being 'asleep at the switch' for
decades by allowing a potentially hazardous compound
to remain in many childhood vaccines, and not forcing
manufacturers to exclude it from new products."
It would not have taken "rocket science" to add up the
amount of exposure as the prescribed number of shots
was increasing, one of the e-mails said.
While asserting that there was no proof of harm, the
U.S. Public Health Service in July 1999 called on manufacturers
to go mercury-free by switching to single-dose vials.
Soon after, Merck introduced a mercury-free version
of its hepatitis B vaccine, replacing the only thimerosal-containing
vaccine it was still marketing at the time, a company
By 2002, thimerosal had been eliminated or reduced to
trace levels in nearly all childhood vaccines. One exception
is the pediatric flu vaccine made by Aventis and still
sold mainly in multi-dose vials.