Site icon VAXOPEDIA

Thimerosal Hype or Hazard

Vincent Iannelli, MD

You know the story about vaccines and thimerosal, right?

Unfortunately for the movie Trace Amounts, simple calling something a fact doesn’t make it a fact. In addition to mischaracterizing how the process started, they seem to think that kids have been getting exposed to even more mercury in vaccines today…

Are you sure?

Thimerosal Timeline

Although it was never actually linked to any significant side effects, as a “precautionary measure,” the AAP recommended that thimerosal (mercury) be removed from childhood vaccines in 1999.

That’s not when the hype over thimerosal started though.

A few years before that, in 1997, an amendment to the Food and Drug Administration (FDA) Modernization Act called on the FDA to compile a list of foods and drugs with added mercury.

“At the time the FDA Modernization Act was passed, it was recommended that infants receive 3 different vaccines that contained thimerosal: diphtheria-tetanus-acellular pertussis (DTaP), hepatitis B, and Haemophilus influenzae type B (Hib). Infants who received all of these vaccines could have been exposed to a cumulative dose of mercury as high as 187.5 μg by 6 months of age. This value exceeded guidelines recommended by the Environmental Protection Agency (EPA) but did not exceed those recommended by the Agency for Toxic Substances Disease Registry (ATSDR) or the FDA.”

Offit et al on Addressing Parents’ Concerns: Do Vaccines Contain Harmful Preservatives, Adjuvants, Additives, or Residuals?

And it was found that in some circumstances, infants could get 187.5 μg of mercury from vaccines by 6 months of age, which exceeded some, but not all regulatory guidelines.

Which regulatory guidelines?

That led to the recommendation from the AAP, in July 1999, to remove thimerosal from vaccines, including the hepatitis B, DTaP, and Hib vaccines, the only routinely used, non-flu vaccines that had ever had thimerosal. Specifically, the AAP asked vaccine manufacturers “for a clear commitment and a plan to eliminate or reduce as expeditiously as possible the mercury content of their vaccines.”

“There is a significant safety margin incorporated into all the acceptable mercury exposure limits. Furthermore, there are no data or evidence of any harm caused by the level of exposure that some children may have encountered in following the existing immunization schedule. Infants and children who have received thimerosal-containing vaccines do not need to be tested for mercury exposure.”

Notice to Readers: Thimerosal in Vaccines: A Joint Statement of the American Academy of Pediatrics and the Public Health Service

It is important to note that thimerosal-free versions of the DTaP and Hib were already available at the time though.

So we had:

And of course, the other vaccines that younger kids got at the time never contained thimerosal, including hepatitis A, MMR, Varivax, polio, and Prevnar.

By January 2003, remaining stocks of vaccines with thimerosal expired.

Also in 2003, thimerosal-free flu vaccines became available, including thimerosal-free flu shots and FluMist, the nasal spray flu vaccine.

Thimerosal Hype or Hazard

So what was the big concern about thimerosal?

It wasn’t that infants were getting exposed to thimerosal in vaccines, but rather that they might get exposed to too much thimerosal.

Looking back at the available vaccines at the time, it is fairly obvious that most infants didn’t get that much thimerosal though, as there were already plenty of thimerosal-free versions of all routinely used vaccines. To get to the higher doses that some folks were concerned about, they would have to get the hepatitis B vaccine, plus thimerosal containing versions of both DTaP and Hib, and a flu shot.

Because young, otherwise healthy children are at increased risk for influenza-related hospitalization, influenza vaccination of healthy children aged 6-23 months is recommended.

Also, keep in mind that it wasn’t until 1991 that hepatitis B and Hib vaccines were added to the immunization schedule to be given to all infants.

And many kids didn’t get flu shots yet.

Remember, it was until the 2004-05 flu season that we started to see strong recommendations to give flu shots to anyone who wasn’t at high risk for complications from the flu. And by that time, thimerosal free flu shots were beginning to appear.

Still, the most important takeaway from all of this is that even though thimerosal was removed from vaccines, it was done as a precautionary measure and not because these kids were harmed. In fact, some kids were harmed in the process, especially as some infants didn’t get their newborn hepatitis B vaccine and at least one went on to get a fatal hepatitis B infection.

What to Know About Vaccines and Thimerosal

Even at the height of the thimerosal scare, most vaccines didn’t contain thimerosal.

More on Vaccines and Thimerosal

Exit mobile version