Fact Sheet - Vaccinations & autism

Childs arm being giving a needle

Vaccinations and autism - extended version

What is the issue?

Autism is a condition that is thought to start before birth but is not always noticed until a child is a toddler. It is often when a child doesn’t learn to talk or interact as expected at about 12 to 18 months old that a difference is first noticed. It is thought that the main causes are genetic but the exact cause is not yet known.

Because the cause of autism isn’t known, there are many theories or ideas about what might be involved. One theory that has had a lot of attention in the media and online is that vaccines might somehow linked to autism. Two main areas are talked about the most: the Measles-Mumps-Rubella (MMR) immunisation and the small amounts of a type of mercury that used to be used to stop vaccines from going off. 

These two issues (the MMR and the concerns about mercury) are different and so will be talked about separately in this fact sheet.

What are the concerns?

  1. MMR
    The MMR jab is given to children in Australia in 2 doses, at 12 months and again at 4 years. A possible link between autism and the MMR gained widespread publicity based on a small study of children with gastrointestinal symptoms and behaviour abnormalities by Andrew Wakefield>

    [1] and a number of other researchers[2]. In a press conference following the publication of the paper, Dr Wakefield further discussed a proposed link between the MMR and autism and suggested there was a case for splitting the vaccine into its component parts (that is, separate measles, mumps and rubella vaccinations)[3] . The main proposed idea was that MMR causes a persistent measles infection in the gut, leading to “leaky-gut” syndrome, which in turn allows inadequately processed peptides from gluten and casein to enter the bloodstream and brain producing an opioid effect[4]. An alternative pathway is that the measles virus itself invades the brain and triggers an immune response resulting in inflammation in the brain, causing autism[5].

  2. Mercury (Thiomersal)

    Thiomersal (also known as thimerosal) was added to vaccines in the 1940s as a preservative and contains ethylmercury. Mercuryis known to cause neurological damage[6], and while ethylmercury is considered less harmful than methylmercury, the suggestion is that small amounts in vaccines, combined with the increased number of compulsory vaccines since the early 1990s[7] are causing autism and other developmental and neurological problems. There appears to be more than one causal mechanism proposed for the thiomersal-autism link, with some authors suggesting that the signs of autism are similar to symptoms of mercury poisoning[8], while others have suggested that thiomersal weakens the immune system allowing the live virus contained in the MMR to persist and damage the gut and brain[9].

What does the research say?

  1. MMR
    Wakefield’s original research has been criticised on a number of grounds. Following publication, the paper was criticised for using adult or other non-standard rather than paediatric ranges on some laboratory tests, meaning that some of the gastrointestinal findings were in fact not abnormal10],[11]. It was also found that there was a link between Dr Wakefield and a legal action by parents of some of the children in the study against makers of the MMR. The journal that published the article, The Lancet,   suggested that this link should have been known to help inform whether the paper should have been published in the first place[12],[13]. Ten of the thirteen original authors of the paper issued a partial retraction in 2004, suggesting there was no causal link established between the MMR and autism[14]. In 2010, The UK General Medical Council[15] found Wakefield had displayed serious professional misconduct on numerous occasions in relation to his research. As a result of these findings Wakefield, was removed from the medical register and the Lancet issued a full retraction of the paper in February 2010[16].

    A number of large population studies have found no evidence to support a causal association between MMR and autism. A study of more than 500,000 Danish children[17] found no increased risk of ASDs among those who had received the MMR compared with those who had not been vaccinated, and even though autism rates increased during the study period, this increase occurred well after the introduction of the MMR vaccine.

    Similarly, Fombonne and colleagues[18] study in 2006 of more than 27,000 Canadian children noted that rates of Pervasive Developmental Disorders (PDDs) increased over time, while take-up of the MMR vaccination decreased which ruled out a causal association between ASD and the MMR. Another study[19]  also found that even when the MMR was discontinued in a region of Japan, autism rates continued to rise, suggesting that the MMR vaccine was unlikely to be the main cause of autism. Similarly, a more recent study of Japanese children[20] did not find convincing evidence that MMR vaccination was associated with an increased risk of ASD

    In an attempt to replicate part of Wakefield’s findings, a study in 2008[21] compared bowel tissue of 25 children’s autism and gastrointestinal symptoms, with 13 children with gastrointestinal symptoms alone. The researchers found no differences between the two groups.

    In 2010, more research[22] found that autism risk was actually lower in children who were vaccinated with the MMR than in children who were unvaccinated.
     

  2. Mercury (Thiomersal)
    Mercury, in the form of methylmercury, has well documented links to neurological disorders, but ethylmercury, the type of mercury previously used in vaccines, has less potential for harm[23]. Studies of whole populations also provide information about the thiomersal-autism theory. The Fombonne et al (2006) study mentioned previously, also examined links between autism rates and links with thiomersal. Because there were different immunisation schedules over time, children received different amounts of exposure to thiomersal and the children could be looked at in three groups – children who had medium exposure, children with high exposure and children whose vaccinations contained no thiomersal at all. More cases of PDD were found in the group that had no exposure to thiomersal, leading them to rule out an association between PDDs and thiomersal.

    Another study[24] also looked at rates of autism before and after the removal of thiomersal from vaccines in California and found no decrease in diagnosis and a similar recent study[25]  also looked at thiomersal exposure and found no evidence that higher thiomersal exposure was associated with increased risk of autism.

    In addition, it is important to note that thiomersal has been removed from all childhood vaccines, with the exception of one of the Hepatitis B vaccinations (Australia) and an influenza vaccine (US) in 2001[26].

In summary

While there have been concerns that vaccines cause autism, large scale studies have not found a link between autism and the MMR vaccine, or autism and the mercury-based preservative thiomersal.

Australian information about vaccinations and a decision making guide for parents regarding the MMR is provided by the National Centre for Immunisation Research & Surveillance (NCIRS), at www.ncirs.edu.au/immunisation/education/mmr-decision/index.php

 

 

[1] Wakefield, A.J., Murch, S.H., Anthony, A., Linnell, J. et al. (1998). Ileal-lymphoid-nodular hyperplasia, non- specific colitis and pervasive developmental disorder in children. The Lancet, 351 (9103), 637 – 641.

 

[2] Campion, E.W. (2002). Suspicions about the safety of vaccines. The New England Journal of Medicine, 347(19), 1474 – 1475

[3] Horton, R. (2004). A statement by the editors of The Lancet. The Lancet, 363 (9411), 820 – 821.

[4] Fitzpatrick, M. (2004). MMR: Risk, choice, chance. British Medical Bulletin, 69, 143–153.

[5] Office of Special Masters. (2009). Michelle Cedillo v. Secretary of Health and Human Services. No. 98-916V. Retrieved April 17, 2009 from: www.ccandh.com/decisions/cedillo.pdf.

[6] Baker, J.P. (2008). Mercury, vaccines & autism: One controversy, three histories. American Journal of

Public Health, 98 (2), 244 – 253.

[7] Generation Rescue (2009). Is it the mercury? Retrieved April 17, 2009, from: http://generationrescue.org/isit.html

[8] Bernard, S. Enayati, A. Redwood, L. Roger, H. & Binstock, T. (2001). Autism: A novel form of mercury poisoning. Medical Hypotheses, 56 (4), 462–471.

[9] Office of Special Masters. (2009). Michelle Cedillo v. Secretary of Health and Human Services. No. 98-916V. Retrieved April 17, 2009 from: www.ccandh.com/decisions/cedillo.pdf.

[10] Sinclair, L. (1998). Autism, inflammatory bowel disease & MMR vaccine (correspondence). The Lancet, 351 (1355).

[11] Richmond, P. & Goldblatt, D. (1998). Autism, inflammatory bowel disease & MMR vaccine (correspondence). The Lancet, 351(1355).

[12] Horton, R. (2004). A statement by the editors of The Lancet. The Lancet, 363 (9411), 820 – 821.

[13] Deer, B. (2009). MMR doctor Andrew Wakefield fixed data on autism. Times Online, February 8, 2009. Retrieved April 2, 2009, from: www.timesonline.co.uk/tol/life_and_style/health/article5683671.ece

[14] Murch, S.H., Anthony, A., Casson, D.H., Malik, M., Berelowitz, M., Dhillon, A.P., Thomson, M.A., Valentine, A., Davies, S.E., Walker-Smith, J.A. (2004). Retraction of an interpretation. The Lancet, 363 (9411), 750.

[15] General Medical Council (2010). Andrew Wakefield: determination on serious professional misconduct and sanction 24 May 2010. Retrieved May 15, from: www.gmc-uk.org/Wakefield_SPM_and_SANCTION.pdf_32595267.pdf

[16] The Lancet. (2010). Retraction—Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. The Lancet, 375(9713), 445.

[17] Madsen, K.M., Hvid, A., Vestergaard, M., Schendel, D., Wohlfahrt, J., Thorsen, P., Olsen, J. & Melbye, M. (2002). A population-based study of measles, mumps and rubella vaccination and autism. The New England Journal of Medicine, 347(19), 1477 – 1482.

[18] Fombonne, E., Zakarian, R., Bennett, A., Meng, L. & McLean-Heywood, D. (2006). Pervasive developmental disorders in Montreal, Quebec, Canada: Prevalence & links with immunisations. Pediatrics, 118(1), e139 – e150.

[19] Honda, H., Shimizu, Y. & Rutter, M. (2005). No effect of MMR withdrawal on the incidence of autism: a total population study. Journal of Child Psychology and Psychiatry, 46(6), 572 – 579.

[20] Uno, Y., Uchiyama, T., Kurosawa, M., Aleksica, B. & Ozakia, N. (2012). The combined measles, mumps, and rubella vaccines and the total number of vaccines are not associated with development of autism spectrum disorder: The first case–control study in Asia. Vaccine, 3(28), 4292–4298.

[21] Hornig, M., Briese, T., Buie, T., Bauman, M.L., Lauwers, G. et al. (2008). Lack of association between measles virus vaccine and autism with enteropathy: A case-control study. PLoSONE, 3(9), e3140.

[22] Mrożek-Budzyn, D., Kiełtyka, A., Majewska, R. (2010). Lack of association between measles-mumps-rubella vaccination and autism in children: A case-control study. Pediatric Infectious Disease Journal,129(5), 397 – 400.

[23] National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases (NCIRS) (2005). Thiomersal fact sheet. Retrieved September 5, 2009, from: www.ncirs.usyd.edu.au/facts/f-thiomersal.html.

[24] Schechter, R. & Grether, J.K. (2008). Continuing increases in autism reported to California’s developmental services system: Mercury in retrograde. Archives of General Psychiatry, 65(1), 19 – 24.

[25] Price, C.S., Thompson, W.W., Goodson, B., Weintraub, E.S., Croen, L.A., Hinrichsen, V.L., Marcy, M., Robertson, A., Eriksen, E., Lewis, E., Bemel, P., Shay, D., Davis, R.L. & DeStefano, F. (2010). Prenatal and infant exposure to thimerosal from vaccines and immunoglobulins and risk of autism. Pediatrics, 126, 656 – 664.

[26] National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases (NCIRS) (2005). Thiomersal fact sheet. Retrieved September 5, 2009, from: www.ncirs.usyd.edu.au/facts/f-thiomersal.html.

 

(Reviewed in November 2016)