Misconceptions about Immunization

Misconception #9:
Vaccines cause autism

On October 3, 1999, Cable News Network aired a program on which the parents of three-year-old Liam Reynolds stated that he had developed autism two weeks after receiving measles, mumps and rubella (MMR) vaccine [1]. The program included the views of Stephanie Cave, M.D., a Louisiana physician who "specializes in treating autism" with diet and nutritional supplements [2]. An American Academy of Pediatrics official and explained why there was no reason to believe that a link exists between autism and vaccination. But the dramatic before-and-after videotapes of the child probably had enough impact to persuade many parents to avoid having their children vaccinated. The program's narrator stated there had been "a puzzling jump in the number of children being diagnosed with autism." However, the number being diagnosed may reflect increased reporting of cases rather than an increase in actual incidence.

Autism is a chronic developmental disorder characterized by problems in social interaction, communication, and restrictive and repetitive interests and activities. Autism may be initially noted in infancy as impaired attachment, but it is most often first identified in toddlers, mostly boys, from 18 to 30 months of age. Boys are 3-4 times more likely to be afflicted with autism than girls. Girls as a group, however, may be more severely affected. Correct diagnosis of autism depends on an accurate developmental history focused on types of behaviors typical of autism and on evaluation of functional skills. Approximately 75% of persons with autism are mentally retarded. Fewer than 5% of children with autistic traits have fragile X or another known chromosomal abnormality. Although no cure exists, autism is treatable. Symptoms associated with autism often improve as children start to acquire language and learn how to communicate their needs.

In most cases of autism, no cause is apparent. In a few cases, biologic causes have been identified, although none are unique to autism. Some prenatal factors include intrauterine rubella; tuberous sclerosis; chromosomal abnormalities, such as Down's syndrome; as well as brain abnormalities, such as hydrocephalus. Frequently cited postnatal conditions associated with autism are untreated phenylketonuria, infantile spasms, and herpes simplex encephalitis. In the majority of cases, however, no underlying cause can be identified.

The current theory favored by many experts is that autism is a genetically-based disorder that occurs before birth [3]. Studies of persons with autism are finding abnormalities in brain structures that develop in the first few weeks of fetal development [4]. Evidence that genetics is an important, but not exclusive, cause of autism includes a 3-8% risk of recurrence in families with one affected child. A working group convened by the National Institutes of Health in 1995 reached a consensus that autism is a genetic condition. An issue unresolved by the group was the role of immune factors in autism spectrum disorders; it was suggested that studies to clarify the situation are needed.

No Evidence of Link

Some parents of children with autism believe that there is a link between measles, mumps, rubella (MMR) vaccine and autism. However, there is no sensible reason to believe that any vaccine can cause autism or any kind of behavioral disorder. Typically, symptoms of autism are first noted by parents as their child begins to have difficulty with delays in speaking after age one. MMR vaccine is first given to children at 12-15 months of age. Since this is also an age when autism commonly becomes apparent, it is not surprising that autism follows MMR immunization in some cases. However, by far the most logical explanation is coincidence, not cause-and-effect.

If measles vaccine or any other vaccine causes autism, it would have to be a very rare occurrence, because millions of children have received vaccines without ill health effects. The only "evidence" linking MMR vaccine and autism was published in the British journal Lancet in 1998 [5]. An editorial published in the same issue, however, discussed concerns about the validity of the study [6]. Based on data from 12 patients, Dr. Andrew Wakefield (a British gastroenterologist) and colleagues speculated that MMR vaccine may have been the possible cause of bowel problems which led to a decreased absorption of essential vitamins and nutrients which resulted in developmental disorders like autism. No scientific analyses were reported, however, to substantiate the theory. Whether this series of 12 cases represent an unusual or unique clinical syndrome is difficult to judge without knowing the size of the patient population and time period over which the cases were identified. If there happened to be selective referral of patients with autism to the researchers' practice, for example, the reported case series may simply reflect such referral bias. Moreover, the theory that autism may be caused by poor absorption of nutrients due to bowel inflammation is senseless and is not supported by the clinical data. In at least 4 of the 12 cases, behavioral problems appeared before the onset of symptoms of inflammatory bowel disease. Furthermore, since publication of their original report in February of 1998, Wakefield and colleagues have published another study in which highly specific laboratory assays in patients with inflammatory bowel disease, the posited mechanism for autism after MMR vaccination, were negative for measles virus [7,8].

Other recent investigations also do not support a causal association between MMR (or other measles-containing vaccines) and autism or inflammatory bowel disease (IBD) [9-13]. In one investigation, a Working Party on MMR Vaccine of the United Kingdom's Committee on Safety of Medicines (1999) was charged with the evaluation of several hundred reports, collected by a firm of lawyers, of autism, Crohn's disease, or similar disorders developing after receipt of MMR or MR vaccines. The Working Party conducted a systematic, standardized review of parental and physician information. Although acknowledging that it is impossible to prove or refute the suggested associations (because of variable data quality, biased selection of cases, and lack of a control group), the Working Party concluded that the information available "... did not support the suggested causal associations or give cause for concern about the safety of MMR or MR vaccines." [12] In March 2000, a Medical Research Council report concludes that between March 1998 and September 1999 no new evidence had suggested a causal link between MMR and autism or IBD [13]. The American Medical Association has reached the same conclusion.

A study by Taylor and colleagues provides population-based evidence that overcomes many of the limitations faced by the Working Party and by Wakefield and colleagues [14,15]. The authors identified all 498 known cases of autism spectrum disorders (ASD) in certain districts of London born in 1979 or later and linked them to an independent regional vaccination registry. ASD includes classical autism, atypical autism, and Asperger's syndrome, but the results were similar when cases of classical autism were analyzed separately. The authors noted:

A study of the population of children in two communities in Sweden also found no evidence of an association between MMR vaccination and autism [16]. That study found no difference in the prevalence of autism in children born after the introduction of MMR vaccination in Sweden compared with children born before.

In January 1990, an Institute of Medicine committee examining possible health effects associated with DPT vaccine concluded that there was no evidence to indicate a causal relation between DPT vaccine or the pertussis component of DPT vaccine and autism [17]. Also, data obtained from CDC's Monitoring System for Adverse Events Following Immunization (MASAEFI) system, showed no reports of autism occurring within 28 days of DPT immunization from 1978-1990, a period in which approximately 80.1 million doses of DPT vaccine were administered in the United States. From January 1990 through February 1998, only 15 cases of autism behavior disorder after immunization were reported to the Vaccine Adverse Events Reporting System (VAERS). Because of the small number of reports over an 8-year period, the cases reported are likely to represent unrelated chance occurrences that happened around the time of vaccination. The most frequent vaccines cited in the reports were diphtheria, tetanus, pertussis (DPT), oral polio vaccine (OPV), and MMR. Other vaccines reported as having a possible association with autism were Haemophilus influenzae type B and Hepatitis B.

In 2000, the American Academy of Pediatrics convened a multidisciplinary panel of experts ro review what is known about the development, epidemiology, and genetics of ASD and the hypothesized associations with IBD, measles, and MMR vaccine. The panel concluded:

Although the possible association with MMR vaccine has received much public and political attention and there are many who have derived their own conclusions based on personal experiences, the available evidence does not support the hypothesis that MMR vaccine causes autism or associated disorders or IBD. Separate administration of measles, mumps, and rubella vaccines to children provides no benefit over administration of the combination MMR vaccine and would result in delayed or missed immunizations. Pediatricians need to work with families to ensure that children are protected early in the second year of life from these preventable diseases. Continued scientific efforts need to be directed to the identification of the causes of ASD [18].

The fact that autism is diagnosed during the second or third year of life does not mean that it began at that age. Analyses of home movies made from birth onward have shown that most children who are diagnosed as autistic during the second or third year have abnormal signs during the first year—and some even show abnormalities at birth [19-26].

Recently, the National Childhood Encephalopathy Study (NCES) was examined to see if there was any link between measles vaccine and neurological events. Researchers in England found no indication that measles vaccine contributes to the development of educational and behavioral deficits or other possible signs of long-term neurological damage [27].

Most people have no adverse reaction after receiving a MMR vaccination. About 5%-15% of vaccines may develop a fever 5-12 days after MMR vaccination and 5% may develop a rash. Central nervous system conditions, including encephalitis and encephalopathy, have been reported with a frequency of less than one per million doses administered. In July 2002, after Wakefield testified before a U.S. Congressional committee chaired by a vaccine opponent, Dr. Michael Fitzpatrick (a British general physician and parenbt of an autistic child) charged that Wakefield "has opted out of medical science to join the world of pseudoscientific dogma, media celebrity and populist campaigning." [29] In a devastating review of the conduct of Wakefield and Paul Shattock, a pharmacist and vaccine opponent who runs the so-called Autism Research Unit at the University of Sunderland, Fitzpatrick stated:

There is now a flourishing network of private laboratories offering urine and blood tests of the sort carried out by Mr Shattock—all of no recognised diagnostic value. There is a substantial business sector selling dietary supplements, vitamins, minerals, enzymes and all manner of special dietary products —all of no proven therapeutic value. The common feature of both tests and supplements is their exorbitant cost, suggesting that high profits are being made from peddling interventions of no proven value, often to desperate parents, many on low incomes.

There are other beneficiaries of the anti-MMR campaign. Private GPs are now making profits of several hundred percent from selling separate vaccines. Lawyers are eagerly collecting legal aid fees by inflating the hopes of parents that they may gain substantial compensation for the alleged damages from MMR through the pursuit of litigation. It is not surprising that both are enthusiastic supporters of Dr Wakefield's crusade. It seems that Britain's investigative journalists are so smitten by Dr Wakefield's charisma and so credulous towards junk science, that they are reluctant to investigate the real abuses generated around the anti-MMR campaign [29].

As with the administration of any agent that can produce fever, some children may have a febrile seizure. Most that follow measles vaccination are simple febrile seizures and affect children without known risk factors. An increased risk of febrile convulsions may occur among children with a prior history of convulsions.

The Bottom Line

There are no proven data to suggest that measles vaccine will increase the risk of developing autism or any other behavioral disorder [28]. The known benefits vastly exceed any unknown risks. The CDC continues to recommend two doses of MMR vaccine for all children who do not have a known medical contraindication; the first dose is recommended at 12-15 months of age and the second dose is recommended at either 4-6 years of age or at 11-12 years of age [30,31].

To assure the safety of vaccines, the CDC, the FDA, the National Institutes of Health (NIH), and other federal agencies routinely examine any new evidence that would suggest possible problems with the safety of vaccines. Currently, CDC is conducting a study in the metropolitan Atlanta area to further evaluate any possible association between MMR vaccination and autism.

Immunization against measles has led to a dramatic decrease in the incidence of measles, which is sometimes fatal. I believe that the manner in which CNN covered this issue was extremely irresponsible and will result in the death of children whose parents are scared out of having their children receive it.

For Additional Information.

References

  1. A question of harm. CNN & Time broadcast, Oct 3, 1999.
  2. Liam's mother Shelley H. Reynolds founded and serves as president of Unlocking Autism, an organization intended to "bring the issues of autism from individual homes to the forefront of national dialogue." Dr. Cave is a board member described on the Web site as "a leader and a fighter for the alternative therapies that seem to work with many of our children. She believes in using drugs as a last resort, concentrating instead on ascertaining the unique biochemistry of each individual child and working to achieve a balance through nutritional supplements and dietary interventions." The idea that autism represents a nutritional imbalance is preposterous.
  3. Piven J. The biological basis of autism. Current Opinion in Neurobiology 7:708-712, 1997.
  4. Rodier PM, Hyman SL. Early environmental factors in autism. MRDD Research Reviews 5:121-128, 1998.
  5. Wakefield AJ and others. Ileal lymphoid nodular hyperplasia, non-specific colitis, and regressive developmental disorder in children. Lancet 351:637-641, 1998.
  6. Chen RT, DeStefano F. Vaccine adverse events: Causal or coincidental? Lancet 351:611-612, 1998.
  7. Chadwick N and others. Measles virus DNA is not detected in inflammatory bowel disease using hybrid capture and reverse transcriptase followed by polymerase chain reaction. Journal of Medical Virology 55:305-311, 1998.
  8. Duclos P, Ward BJ. Measles vaccines: A review of adverse events. Drug Safety 19:435-454, 1998.
  9. Afzal MA and others. Absence of measles-virus genome in inflammatory bowel disease. Lancet 351:646, 1998.
  10. Ekbom A and others. Perinatal measles infection and subsequent Crohn's disease. Lancet 344:508-510, 1994.
  11. Metcalf J. Is measles infection associated with Crohn's disease? British Medical Journal 316:561, 1998.
  12. Medicines Commission Agency/Committee on Safety of Medicines. The safety of MMR vaccine. Current Problems in Pharmacovigilance 25:9-10, 1999.
  13. McGregor AM and others. Report of the Strategy Development Group Subgroup on Research into Inflammatory Bowel Disorders and Autism. London: Medical Research Council, March 2000.
  14. Taylor B and others. Autism and measles, mumps, and rubella vaccine: No epidemiological evidence for a causal association. Lancet 353:2026-2029, 1999.
  15. DeStefano F, Chen RT. Negative association between MMR and autism. Lancet 353:1987-1988, 1999.
  16. Gillberg C, Coleman M. Autism and medical disorders: A review of the literature. Developmental Medicine and Child Neurology 38:191-202, 1996.
  17. Howson CP and others, editors. Adverse Effects of Pertussis and Rubella Vaccines, Washington, DC: National Academy Press, 1991.
  18. Halsey NA and others. Measles-mumps-rubella vaccine and autistic spectrum disorder: Report from the New Challenges in Childhood Immunizations Conference Convened in Oak Brook, Illinois, June 12-13, 2000. Pediatrics 107(5):E84, 2001.
  19. Adrien JL and others. Autism and family home movies: preliminary findings. Journal of Autism and Developmental Disorders 21:43-49, 1991. PMID: 2037548
  20. Adrien JL and others. Blind ratings of early symptoms of autism based upon family home movies. Journal of the American Academy of Child and Adolescent Psychiatry 32:617-626, 1993.
  21. Adrien JL and others. Early symptoms in autism from family home movies. Evaluation and comparison between 1st and 2nd year of life using I.B.S.E. scale. Acta Paedopsychiatrica 55:71-75, 1992.
  22. Carmagnat-Dubois F and others. Rett syndrome and autism: Early comparative evaluation for signs of autism using family movies. Encephale 23:273-279, 1997.
  23. Eriksson AS, de Chateau P. Brief report: A girl aged two years and seven months with autistic disorder videotaped from birth. Journal of Autism and Developmental Disorders 22:127-129, 1992.
  24. Mars AE, Mauk JE, Dowrick PW. Symptoms of pervasive developmental disorders as observed in prediagnostic home videos of infants and toddlers. Pediatrics 132:500-504, 1998.
  25. Osterling J, Dawson G. Early recognition of children with autism: a study of first birthday home videotapes. Journal of Autism and Developmental Disorders 24:247-257, 1994.
  26. Teitelbaum T and others. Movement analysis in infancy may be useful for early diagnosis of autism. Proceedings of the National Academy of Sciences U S A 95:13982-13987, 1998.
  27. Zakian A and others. Early signs of autism and family films: A new study by informed evaluators and those unaware of the diagnosis. Encephale 26:38-44, 2000.
  28. Miller D and others. Measles vaccination and neurological events. Lancet 349:730-731, 1997.
  29. Tan LJ. Vaccines do not cause autism. American Medical Association position statement, posted April 3, 2000.
  30. Fitzpatrick M. MMR: MMR: The making of junk science. Spiked Health, July 5, 2002.
  31. Measles prevention: Recommendations of the immunization practices advisory committee. Morbidity and Mortality Weekly Report, Vol.38 , No.S-9, Dec 29, 1989.
  32. Measles, mumps, and rubella-vaccine use and strategies for elimination of measles, rubella and congenital rubella syndrome and control mumps: Recommendations of the advisory committee on immunization practices. Morbidity and Mortality Weekly Report, Vol 47, No. RR-8, May 1, 1998.

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This page was revised on November 17, 2002.