Thiomersal (ethylmercury) containing vaccines

The view of the CHM remains that there is no evidence of neurodevelopmental adverse effects caused by levels of thiomersal in vaccines.  The only evidence of harm due to thiomersal is a small risk of hypersensitivity reactions (that typically include skin rashes or local swelling at the site of injection).  The CHM advises that the balance of risks and benefits of thiomersal-containing vaccines is overwhelmingly positive.

MHRA and CSM statements about the safety of thiomersal-containing vaccines
› Committee on Safety of Medicines (CSM) statement following review of UK epidemiological studies (12 February 2003) and associated CSM summary minutes (25Kb) - On 12 February 2003, the Committee on Safety of Medicines (CSM) considered further evidence which supports the safety of thiomersal (which contains ethylmercury) in vaccines.  The CSM/CHM and their Vaccine Expert Groups have considered further evidence in July and November 2003, in April 2004, July 2005 and April and November 2006.  These data reinforce CSM advice from 2001 that there is no evidence of neurological adverse effects caused by thiomersal in vaccines according to the routine UK immunisation schedule.  The balance of benefits and risks of thiomersal-containing vaccines therefore remains overwhelmingly positive.

› CSM statement (101Kb) 
› CSM Summary minutes (25Kb) 
› CSM Pharmacovigilance Subcommittee (SCOP) minutes September 2001 (168Kb)

The CSM Subcommittee on Pharmacovigilance  also discussed the issue of thiomersal in vaccines and concluded that there was no reliable evidence of neurodevelopmental harm associated with thiomersal in vaccines.

External links*
The Department of Health has produced a fact sheet (external link) which addresses concerns over the safety of thiomersal in vaccines and also answers parents’ questions around the immunisation of their children with thiomersal-containing vaccines.

The European Medicines Agency (EMEA) updated its position statement (external link) on thiomersal in vaccines in March 2004.  It states that:

• The latest epidemiological studies show no association between the vaccination with thiomersal-containing vaccines and specific neurodevelopmental disorders.
• The CPMP re-emphasises that immunisation with vaccines containing thiomersal continues to offer outstanding benefits to the general population, including infants.  The benefits of vaccination far outweigh the risks, if any, of exposure to thiomersal-containing vaccines.
• The CPMP acknowledges that, during some manufacturing processes, the use of organic mercury compounds is necessary and in such cases, residual levels might be present in the final product.

The World Health Organisation (WHO) (external link) - The WHO’s Global Advisory Committee on Vaccine Safety (GACVS) has concluded that the latest pharmacokinetic and developmental studies do not support concerns over the safety of thiomersal in vaccines.

The United States Centers for Disease Control and Prevention (CDC) (external link)

The US Food and Drug Administration (FDA) (external link)
In their response to the citizen’s petition submitted by the Coalition for Mercury-Free Drugs, the FDA have reviewed all the evidence relating to mercury-containing vaccines and medicines.  They conclude that the available evidence supports the view that all currently licensed vaccines and other pharmaceutical drug products that contain thimerosal are safe

› Thiomersal FDA response (176Kb)

The US institute of Medicine (IOM) conducted a review of the safety of thiomersal in vaccines in 2001 and again in 2004.
› Immunization Safety Review: ‘Thiomersal - Containing Vaccines and Neurodevelopmental Disorders’ - 1 October 2001 (external link)
› Immunization Safety Review: ‘Vaccines and Autism’ - 17 May 2004 (external link)
The IOM has concluded that the body of epidemiological evidence favours rejection of a causal relationship between thiomersal-containing vaccines and autism.

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