Thimerosal and other vaccine additives

Abstract

While vaccines would ideally only need to contain the antigens necessary to induce immunity, the reality of vaccine production requires the addition of other materials, sometimes called excipients. These excipients include a wide array of additives, usually in minute concentrations. Preservatives and other related substances are required to maintain vaccine stability and potency. Adjuvants may be necessary to induce adequate protective immunity. In addition, there are other materials sometimes introduced into the final products either as a result of the manufacturing process or packaging. The excipient materials found in vaccines have been a significant source of misunderstanding, and misinformation. Much of the controversy related to vaccine safety is a result of spurious associations between these vaccine additives and exaggerations of real, or perceived, side effects from immunization. While a few of these chemicals can be toxic in large quantities, most are only present in trace amounts in most vaccines. This chapter reviews some of the more common or controversial vaccine excipients, and related information regarding safety concerns.