Is There Mercury in Vaccines?

Paul A. Offit, MD, explains the different types of mercury and how they are processed in the human body. He also discusses which commonly recommended infant vaccines still contain mercury-associated preservatives.


Is there mercury in vaccines?

Paul Offit, MD: Hi, my name’s Paul Offit. I’m talking to you today from the Vaccine Education Center here at The Children’s Hospital of Philadelphia. I think one of the concerns parents have is about a potential additive to vaccines, the preservative mercury. “Is mercury in vaccines?”

And the answer to that question is that mercury is in some multi-dose preparations of the influenza vaccine. The form of mercury is called ethylmercury, and the name of that product is called thimerosal.

Now, one can reasonably be concerned about this knowing that mercury, certainly at high concentrations, can be toxic to the brain, and so-called the central nervous system. But in order to understand, I think, why it is that the mercury that is contained in some multi-dose preparation of the flu vaccine isn’t harmful, I think we need to step back and try and understand mercury in our environment.

Mercury is in the earth’s crust. It has been ever since the formation of the earth. It’s in an inorganic form through things like volcanoes and rock erosions that inorganic mercury comes to the surface of the earth, where it … in soil or on the surface of the seas, it is taken up by bacteria and methylated. So it goes from inorganic mercury to methylmercury. That methylmercury is now organic mercury. It has the capacity to cross cell membranes and do harm.

Now the quantity of methylmercury that’s in the environment is actually far greater than one would ever be exposed to in the mercury that’s in vaccines, which actually isn’t methylmercury; it’s ethylmercury. And it’s a larger molecule. And as a consequence is excreted from the body 10 times more quickly than is methylmercury. So whereas methylmercury accumulates to a far greater extend in the body than ethylmercury, I think parents should be reassured by that.

But I think more reassuring is the fact that just to know that because we all are exposed to methylmercury all the time, and it’s in anything that’s made from water, including breast milk, and including infant formula, that babies are exposed to far more methylmercury in what they drink as young infants, either in formula or in breast milk, than they would ever get from the mercury in vaccines.

Remember the influenza vaccine isn’t given to less than 6-month-old children. So again, there’s no avoiding mercury, and as this true, there is no avoiding many heavy metals in the environment. We all have cadmium, thallium, beryllium, even arsenic in our body. But it’s in quantities far below that that would ever do harm.

Hope that helps, thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Aug 11, 2015