The FDA estimates that it is used in more than 30 licensed vaccines and biologics. Mercury is excreted from the body over time. A. Thimerosal is used as an extra safeguard against contamination. It maybe used during processing or added to the final container to prevent contamination when multi-dose vials are opened. Before Thimerosal was marketed in the United States, a number of safety studies were conducted, first on animals and then on humans.
Thimerosal is an important preservative that protects vaccine against bacterial contamination.
It is very effective in killing bacteria used in several vaccines and in preventing bacterial contamination, particularly in opened multi-dose containers. Some but not all of the vaccines recommended routinely for children in the United States contain thimerosal. Disease outbreaks have occurred following contamination of multi-dose vaccine vials in the United States and from other countries. All vaccines either do not contain thimerosal or contain thimerosal within FDA guidelines. To further increase the margin of safety that already exists, clinicians can use the inherent flexibility in the current immunization schedule to fully vaccinate children and meet even the most conservative guidelines for cumulative mercury exposure.