Re: Why is Thimerosal a necessary component of vaccines?

Ken,

Thanks for the question. Thimerosal is an organomercurial vaccine additive that keeps the product from becoming the source of potentially lethal bacterial infections (if contaminated).

Although I work on vaccine immunology, the inclusion of Thimerisol in vaccines was something that dates way before I started doing research. In fact, it dates earlier than what we know of today regarding antibiotics.

It was first used as a vaccine additive in the 1930s. It was added to keep bacterial growth down and it works. Remember, in the 1930s syphilis was treated by giving patients an arsenic containing compound (arsphenamine), and skin infections were treated with mercurichrome and gentian violet (a violet colored dye that bound to bacteria and either killed them or prevented growth).

The problem with adding antibiotics to vaccines is that the antibiotics can degrade and/or the antibiotics could potentially contribute to developing drug resistant bacteria.

I highly recommend that you visit the web page on this topic that was set up by the Center for Biologics Evaluation and Research CBER. They provide a great deal of useful information about its history and the FDA initiative to begin removing Thimerosal from being a part of new vaccines.

http://www.fda.gov/cber/vaccine/thimerosal.htm