The truth behind Thiomersal (Thimerosal)

What is thiomersal?

Thiomersal is a mercury-containing compound

What are its uses?

Used in the manufacture of some vaccines (especially the opened multi-dose vials) to prevent bacterial and fungal growth.
Used during vaccine production both to inactivate certain organisms and toxins and to maintain a sterile production line.
Used in other products like make-up removers, eye moisturizers, eye shadows, mascaras. Also can be found in soap-free cleansers, antiseptic sprays and topical medications.

Which vaccines contain thiomersal?

Many licensed vaccines do not contain thiomersal. Such vaccines include vaccines in single-dose presentation or vaccines for which thiomersal would interfere with vaccine efficacy such as live vaccines including MMR, oral and inactivated polio, yellow fever, and BCG vaccine.
Other vaccines may contain trace amounts of thiomersal (<0.5 µg per dose), if the preservative has been used in the production process, but has not been added to the final product.
A third group of vaccines have thiomersal added in varying concentrations (10 to 50 µg per dose) as a preservative. Such vaccines include vaccines against diphtheria, tetanus and pertussis (DTP), diphtheria and tetanus toxoids (DT), tetanus toxoid (TT), hepatitis B, Haemophilus influenzae type b (Hib), and influenza.

What is the recommendation of the GACVS on the safety of thiomersal-containing vaccines?

Global Advisory Committee on Vaccine Safety concluded that there is currently no evidence of mercury toxicity in infants, children, or adults exposed to thiomersal in vaccines. The safety of thiomersal-containing vaccines is reviewed at regular intervals.

Is thiomersal the same as methyl mercury?

No. Methyl mercury has the ability to accumulate in the body and to remain there for a long time. Thiomersal contains a different form of mercury (ethyl mercury) which does not accumulate and is metabolized and removed from the body much faster.

Does the influenza vaccine contain thiomersal?

Yes, the majority of influenza vaccines currently contain thiomersal as a preservative.

Is it safe for children to receive an influenza vaccine that contains thiomersal?

Yes. There is no convincing evidence of harm caused by the small amount of thiomersal in vaccines. Most importantly, since 1999, the newly formulated thiomersal preservative-free childhood vaccines (Hepatitis B, Hib, and DTaP) made the maximum total exposure during the first six months of life less than three micrograms of mercury. So, no child will receive excessive mercury from childhood vaccines regardless of whether or not their flu shot contains thimerosal as a preservative.

Is it safe for pregnant women to receive an influenza vaccine that contains thiomersal?

Yes. A study of influenza vaccination examining over 2,000 pregnant women demonstrated no adverse fetal effects associated with influenza vaccine.

Why are some countries withdrawing thiomersal if there is no risk?

Some national public health authorities are striving to replace thiomersal-containing vaccines as a precautionary measure. There is currently no evidence of toxicity from mercury contained in vaccines. The alternatives to thiomersal-containing vaccines are limited and insufficient to cover global needs.