Federal health authorities say science has ruled that out. But to be on the safe side, the U.S. Public Health Service -- along with groups representing pediatricians and family doctors -- urged manufacturers in 1999 to phase thimerosal out of childhood vaccines as soon as possible.
Most such vaccines are now thimerosal-free or contain trace amounts. An exception is the flu shot, which the Centers for Disease Control and Prevention recommends for pregnant women and for infants 6 to 23 months old.
The counter-argument: Why take a risk when thimerosal-free shots are also available and cost just three or four dollars more? The CDC has declined to express a preference for those shots on the theory that there wouldn't be enough to meet demand.
On Monday, as this column reported, a New Mexico pediatrician appeared before the state Board of Pharmacy to urge it to immediately warn residents that most flu shots do have mercury. He also wants the state ultimately to ban it from vaccines for kids and pregnant women, something six states have already done -- with bans taking effect in future years. A dozen states are actively debating the issue.
The pediatrician, Dr. Ken Stoller, said the board decided to seek an advisory opinion from the New Mexico attorney general about its jurisdiction in the matter. It meets again in two months.
"The recent meeting was, I have to confess, a little disappointing from the standpoint of truth-in-labeling as set out in the New Mexico Drug Act," Stoller wrote the board in a follow-up letter.
"I presented clear, accurate and precise information on how a preservative that contains the known neurotoxin, ethylmercury, exists in the flu and other vaccines at a level that exceeds several safety limits as set forth by more than one Federal agency."
Perhaps because of the growing number of state bans -- which mean, self-evidently, that they don't want their children and pregnant women exposed to mercury in flu shots -- the issue is percolating this year in a way that it simply hasn't before.
In a Chicago Tribune piece titled, "A contradiction taints flu shots among infants," writer Julie Deardorff said that as a mom, she was concerned that health experts are now recommending a shot that in most cases contains an ingredient they suggested removing six years ago.
"It was eliminated from nearly all vaccines with one exception: the flu vaccine. Now the academy (American Academy of Pediatrics) wants us to immunize infants with a vaccine that contains an ingredient that it suggests should be removed," Deardorff wrote.
She quotes an Illinois AAP spokesman about the apparent contradiction:
"The amount (of thimerosal) in the multidose influenza vaccine (12.5 micrograms) is well below even the most conservative standards for mercury exposure. ... There's no evidence that thimerosal in vaccines is dangerous, and the benefits kids get from being protected against the flu are substantial."
Still, it needs to be noted that the immunization schedule calls for two 12.5 microgram shots a month apart for the 6-to-23-month olds. That total of is the same amount that was in vaccines some parents believe triggered their child's autism. And some of them believe in utero exposure to mercury via the pregnant mother might be the most dangerous exposure of all.
Directly to the north, a senior chemist at the University of Wisconsin has been trying to get the attention of the Wisconsin Department of Agriculture, Trade and Consumer Protection.
"Unfortunately, in the 35 days that have passed since my original letter, thousands of Wisconsin's most vulnerable citizens have been exposed
to this material (mercury in flu shots)," Michael Wagnitz wrote the department in a letter this week.
"As I explained in my original letter, liquid waste needs to go to a hazardous site if it contains more than 200 ppb mercury. Is it really
safe to inject people with a level of mercury 250 times higher than hazardous waste?
"What exactly is the (department) working on that is more important than stopping the injection of mercury directly into the bloodstreams of its
citizens? Could you give me some examples? Again, I ask that you issue an immediate mercury warning for pregnant women and infants who plan on getting the flu shot."
This looks to be an issue that won't go away.