Thimerosal is a mercury-based preservative, which is used to prevent microbial contamination of vaccines. Most flu vaccines currently used in the United States contain little to no thimerosal, but both the Food and Drug Administration and the CDC say there is no evidence low doses of thimerosal in vaccines cause harm other than minor reactions at the injection site, such as redness or swelling. สล็อต เว็บตรง