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Home , Diphtheria vaccine, Hepatitis B vaccine, Hib vaccine, Pertussis vaccine, Tetanus vaccine, Thiomersal

Immunisation: Myths and Realities supplement and

What is thiomersal? Does thiomersal in vaccines cause

Thiomersal is an organic compound containing poisoning? 49.6% mercury by weight. It is known as In the very low doses contained in vaccines, there ‘thimerosal’ in the USA. One of the chemical is no evidence that thiomersal in vaccines causes names for thiomersal, which best describes . In the body, thiomersal is its composition, is Ethylmercuric converted to , which is thought to be Thiosalicylate. It has been used in very small similar to , but is broken down and amounts in vaccines since the 1930s, as it excreted more rapidly than methylmercury. As prevents bacterial and fungal contamination. such, its potential to cause toxicity is less than that of methylmercury. There is no scientific evidence What is mercury poisoning? that thiomersal in vaccines causes any adverse health effects in children. However, the possibility Most of the scientific information on the harmful exists that of newborn babies, effects of mercury is based on the known effects particularly those who have a low birth weight, with of methylmercury, which is excreted very slowly repeated doses of thiomersal-containing vaccines, from the body. Mercury poisoning can be acute, may result in levels of mercury that are above the but usually results from repeated, chronic recommended guidelines. Theoretically, such exposure to methylmercury. In humans, this is infants may therefore be at risk of adverse effects usually due to eating contaminated foods (mainly from mercury. fish). Mercury poisoning affects the central nervous system, with symptoms such as lethargy, loss of appetite, weight loss, tremor, How much mercury exposure results memory loss, sleep disturbance and confusion. from vaccines? It can also cause inflammation of the gums, Not all vaccines contain thiomersal, and not all loose teeth and a rash. children get all vaccines. In the USA, it was calculated that if all thiomersal-containing vaccines How much mercury causes poisoning? are given, the total exposure to mercury in the first 6 months of life may exceed the EPA guidelines. A Mercury causes poisoning only after it reaches a recent US study measured blood mercury levels certain level in the body. The toxicity depends on before and after a dose of B given the amount of mercury consumed in relation to at birth. This study found raised blood mercury body weight. Therefore, for a fixed amount of levels after vaccination in babies, exposure to mercury, infants are at greater risk particularly premature babies, but the levels were than adults. within the ‘normal’ range defined by the US Different expert bodies have determined that Department of Health and Human Services. safe levels of mercury consumption lie somewhere between 0.7 to 3.3 micrograms of Which childhood vaccines mercury per kilogram of body weight per week. contain thiomersal? The US Environmental Protection Authority (EPA) The current National Health and Medical Research has set the lowest cut-off point at 0.7 Council (NHMRC) Australian Standard Vaccination micrograms of mercury per kilogram of body Schedule for children under the age of 5 years weight per week, and the World Health includes only one vaccine that contains thiomersal. Organization (WHO) has suggested 3.3 This vaccine is monovalent , micrograms per kilogram of body weight per which contains 25 micrograms of thiomersal per week. These levels are considered to be as much dose. However, a thiomersal-free product is now as ten times below the upper safety margin. available. Vaccines that contain hepatitis B in Vaccine Manufacturer Level of thiomersal combination with other vaccines (eg Infanrix-HepB and vaccine CSL 50 micrograms Comvax) do not contain thiomersal. Merck Sharpe Dohme 25 micrograms B OMP (Pedvax Hib, In the past, the only other vaccine containing thiomersal lyophilised/powder form only) that was used in all children under the age of 6 months Hepatitis B (Engerix B) SmithKline Beecham 25 micrograms was Triple (diphtheria--whole cell All influenza vaccines CSL, Aventis Pasteur, 5 – 50 micrograms ). This vaccine was replaced with Ebos, SmithKline Beecham DTPa (diphtheria-tetanus-acellular pertussis vaccine) Japanese encephalitis CSL 35 micrograms by July 1999. The powder-form of Pedvax vaccine (JE Vax) also contained thiomersal. Even if the maximum CSL/Aventis Pasteur 50 micrograms possible number of doses of these vaccines were (Menomune) given, it is unlikely that the WHO recommended limit Q vaccine (Q Vax) CSL 50 micrograms of exposure per kilogram of body weight would have * all other vaccines available in Australia at July 2000 were thiomersal free been exceeded. For information on the Immunise Australia program What is being done to address this issue? Phone the Immunisation Infoline on 1800 671 811 In July 1999, the US Food and Drug Authority (FDA) Visit the Immunise Australia Website on issued a directive to all vaccine manufacturers to http://immunise.health.gov.au remove thiomersal from all vaccines, or to justify its continued use. The Australian Therapeutic Goods Administration (TGA) has written to sponsors of all Further reading vaccines included on the Australian Standard Vaccination Statement on thimerosal by David Satcher, M.D., Ph.D, US Surgeon General, Assistant Secretary for Health, Department of Health and Schedule, requesting removal of thiomersal or Human Services, USA minimisation of thiomersal content. In response, a http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/default.htm thiomersal-free monovalent hepatitis B vaccine was Thimerosal in vaccines: a joint statement of the American Academy of Pediatrics and the Service. Morbidity and Mortality introduced in May 2000, and an equivalent product was Weekly Report 1999;48(26):563–5. introduced in August 2000. It is important to note that, http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/thimerosal- AAP&PHS.htm for babies at high risk of hepatitis B, the risk of hepatitis Centers for Disease Control - Questions and Answers about Thimerosal B is far greater than the risk of thiomersal, and http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/thimerosal.htm vaccination should not be delayed in this group. Recommendations regarding the use of vaccines that contain thimerosal as a . Morbidity and Mortality Weekly Report 1999;48(43):996–8. What about vaccines for adults? http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/mm4843a4.htm Halsey NA. Limiting infant exposure to thimerosal in vaccines and other The levels of mercury in adults resulting from sources of mercury [editorial]. Journal of the American Medical Association 1999;282(18):1763–6. thiomersal-containing vaccines (such as influenza From the Centers for Disease Control and Prevention. Availability of vaccine) are so low that expert bodies do not hepatitis B vaccine that does not contain thimerosal as a recommend any change in policy. preservative. Journal of the American Medical Association 1999;282(13):1219–20. Clements CJ, Ball LK, Ball R, Pratt D. Thiomersal in vaccines. Lancet Vaccines containing thiomersal, July 2000* 2000;355:1279–1280. Stajich GV, Lopez GP, Harry SW, Sexson WR. IIatrogenic exposure to mercury after hepatitis B vaccination in preterm infants. J Pediatrics Vaccine Manufacturer Level of thiomersal 2000;136: 679–681. DTPw (Triple Antigen) CSL 50 micrograms Combined diphtheria and CSL 50 micrograms (CDT) Adult diphtheria and CSL 50 micrograms tetanus vaccine (ADT)

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