Adjuvants and Thimerosal (aka Thiomersal)

Adjuvants stimulate increased, nonspecific immunity and are included in many "killed" vaccines. Until October 16, all adjuvants in licensed vaccines in the US were aluminum salts. They are included in tetanus, Hepatitis A and B, anthrax and other killed vaccines.

Thimerosal is a compound composed of 50% mercury which has been included in many killed vaccines to prevent growth of contaminating microorganisms. Due to concerns about its known toxicities, and the large doses of injected mercury that were administered when children received multiple vaccines on the same day, it was mostly (apart from flu vaccines) removed from US vaccines starting 10 years ago. Most currently available, killed vaccines only include about 5% of the amount of thimerosal they previously contained, or one microgram of mercury per dose. Some flu vaccines still contain 25 mcg mercury. Pandemrix contains 5 micrograms of thimerosal.

ASO4 is a more powerful adjuvant mixture than the currently used aluminum salts. Here is the package insert. The approval of the first novel adjuvant (containing MPL, not squalene) in a licensed US vaccine will open the floodgates to many new vaccines now in development, which contain ASO3, ASO4 and other powerful adjuvants.

Now that Cervarix is approved, the public can gain access to the data used to support licensure via Freedom of Information Act requests.