Vaccines have been our “saving grace” ever since their discovery, and with technological and medical advancement, even more so. If you want to read more about the history of vaccines, check out the post here. Even though immunization is widely recognized as one of the greatest achievements of public health due to its success and cost-effectiveness, the components of vaccines have come under heavy scrutiny [1]. This myth will be focusing on Thimerosal, a mercury-based preservative used to prevent germs (like bacteria and fungi) from contaminating multi-dose vials of vaccines.
Since mercury consumption was being linked to central nervous system (CNS) damage, lawmakers, environmentalists, medical, and public health workers in the late 1990s became concerned about environmental exposures to mercury, particularly from consumption of fish. Due to this, in 1999, the U.S. Food and Drug Administration (FDA) requested that drug companies report on amounts of mercury in their products [2].
As Thimerosal contains mercury, people are worried that vaccines containing this compound will lead to CNS damage, and in turn, autism.
The Truth
As FDA requested to report mercury levels, scientists have declared the amount of mercury in vaccines containing Thimerosal. These amounts do not exceed FDA guidelines, and are significantly lower than the amount of mercury found in fish[2].
Even though research showed no link between the controlled amount of mercury in vaccines and autism, Thimerosal was removed from childhood vaccines between 1999 and 2001. Today, even the flu shot has a Thimerosal-free alternative. It is important to note that Thimerosal has never been used in live vaccines as an antimicrobial agent [3]. For more information about the different types of vaccines, check out this post.
Despite the fact that Thimerosal-free alternatives were created, there have been nine CDC-funded or conducted studies since 2003 that have found no link between Thimerosal-containing vaccines and autism. These studies also found no link between measles-mumps-rubella (MMR) vaccine and autism in children [4], more on this topic next week.
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Written by: Phaedra
Edited by: María and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. For more information about vaccines and their safety profile, please see previous posts or consult with your personal physician. If you have any questions about this topic, please comment or send them to our email.
References:
Dubé, E., Vivion, M. and MacDonald, N. (2014) “Vaccine hesitancy, vaccine refusal and the anti-vaccine movement: influence, impact and implications”, Expert Review of Vaccines, 14(1), pp. 99-117. Available at: https://pubmed.ncbi.nlm.nih.gov/25373435/
Thimerosal and Vaccines. US Food and Drug Administration (2019). Available at: https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/thimerosal-and-vaccines (Accessed: 9th December 2021)
Thimerosal in vaccines. World Health Organization (2006). Available at: https://www.who.int/teams/health-product-policy-and-standards/standards-and-specifications/vaccine-standardization/thiomersal (Accessed: 9th December 2021)
Science summary: CDC Studies on Thimerosal in Vaccines. Centers for Disease Control and Prevention (2021). Available at: https://www.cdc.gov/vaccinesafety/pdf/cdcstudiesonvaccinesandautism.pdf (Accessed: 9th December 2021)
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