Thimerosal : facts and controversy

Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2015The issue of thimerosal-containing vaccines as a possible cause of autistic and neurodevelopmental disorders has been a controversial topic since 1999(1). Although concerns have been voiced about its use, the mercury-based preservative Thimerosal remains the most widely used chemical form of organic mercury (Ethylmercury) in medicine(2). Mercury is a known toxicant affecting mainly the central nervous, renal, cardiovascular and immune systems(3) and although Thimerosal has been banned in several countries, it continues to be added to some vaccines routinely given to young children and pregnant women in the United States(4). In the 1970s, only one vaccine contained Thimerosal (5) and based on that fact, a formal review by the FDA concluded that no dangerous quantity of mercury was likely to be received from vaccines over a lifetime.(5) Even though Thimerosal exposure increased tremendously over the years, the FDA's conclusions of 1976 were unquestioned by the medical and governmental authorities until the late 1990s (6). During this time and until 1999 the overwhelming consensus was that ethylmercury in low concentrations was safe and effective in practice. This review focuses on the clinical, epidemiological, and toxicological studies of adverse effects of Thimerosal and examines the outcomes of acute Ethylmercury poisoning to assess the potential link between thimerosal-containing vaccines and severe adverse neurological effects and by doing so, evaluate whether that evidence suggests accepting or rejecting the hypothesis