Vaccines and Autism: A Case Study
Transcript of Vaccines and Autism: A Case Study
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Vaccines and Autism:A Case Study
Alison Taylor
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Autism
• Neurological and DevelopmentalDisorder
• Autism Spectrum Disorders• Symptoms
― Language― Social Behaviors― Repetitive-Restrictive Behavior
http://commons.wikimedia.org/wiki/File:Autism-stacking-cans_edit.jpg
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Incidence Rates of Autism
Barbaresi et al., 2009 (Pubmed Central)
Olmsted County, Minnesota
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Genetics and Environment: Human Disorders
GENETIC MIXED ENVIRONMENTAL
Sickle cellanemia
VitaminDeficiencyCancer
http://commons.wikimedia.org/wiki/File:Sicklecells4.jpg, http://commons.wikimedia.org/wiki/File:Scorbutic_tongue.jpghttp://commons.wikimedia.org/wiki/File:Carcinoma_microcellulare_oatcell_carcinoma_or_anaplastic_carcinoma_%28lung%29H%26E_magn_200x.jpg
AUTISM
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Genetics of Autism
Siblings 4.5%
Fraternal Twins0-10%
Identical Twins70-90%
Information Source: Abrahams and Geschwind, 2008
UnrelatedChildren
<1%
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The Beginning of the Vaccines & Autism Debate
(1998) Wakefield study suggesting a correlation betweenreceiving the MMR vaccine and displaying behavioralsymptoms of autism
(1999) US Public Health Service and American Academy ofPediatrics recommend removing thimerosal from vaccinesas much as possible
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The Beginning of the Vaccines & Autism Debate
(1998) Wakefield study suggesting a correlation betweenreceiving the MMR vaccine and displaying behavioralsymptoms of autism
(1999) US Public Health Service and American Academy ofPediatrics recommend removing thimerosal from vaccinesas much as possible
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MMR Vaccine – Autism Hypothesis
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Wakefield Study: Study Design
• 12 children• Parents or doctors
reported GI symptoms andautism near administrationof MMR vaccine
• Samples were taken toconfirm GI symptoms
Information source: Wakefield et al., 1998
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Wakefield Study: Study Flaws
• Small Number• Case Report• Patient Testimonial• Selection Bias• Confounding factors• Ethical Concerns• Does not prove hypothesis
“We did not prove an association between measles, mumps,and rubella vaccine and the syndrome described.”
Information source: Wakefield et al., 1998
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Wakefield Study: Study Flaws
• Small number• Case report• Patient Testimonial• Selection Bias• Confounding factors• Ethical Concerns• Does not prove hypothesis
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Denmark Study: Study Design
Number ofChildren in Study
Number of AutismCases
Number per10,000
Total 537,303 316 5-6/10,000
Vaccinated 440,655 263 5-6/10,000
Not vaccinated 96,648 53 5-6/10,000
Information Source: Madsen et al., 2002
• Age at vaccination – No effect• Interval since vaccination – No effect• Date of vaccination – No effect• Confounders: Sex, Birth weight, Gestational age,
Socioeconomic status, Age at diagnosis
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More Recent Studies
• Larger Numbers• Retrospective Studies• No Selection Bias• No Ethical Concerns
According to the Institute of Medicine:-Evidence rejects the connection between the MMR vaccineand autism
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The Beginning of the Vaccines & Autism Debate
(1998) Wakefield study suggesting a correlation betweenreceiving the MMR vaccine and displaying behavioralsymptoms of autism
(1999) US Public Health Service and American Academy ofPediatrics recommend removing thimerosal from vaccinesas much as possible
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Thimerosal – Vaccine Hypothesis
Mercury Level
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TCVs and Autism: Conclusions
Points about TCVs and Autism:-Methylmercury is known to be toxic, but thimerosal contains
ethylmercury-Source of methylmercury: certain fish-Thimerosal has been safely used in vaccines since the 1930s
According to the Institute of Medicine:-Evidence rejects the connection between the thimerosal
containing vaccines and autism
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Media AdvocacyGroups
Why is there still a debate?
Public Figures
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Summary: Vaccines and Autism
• Explained genetic component of autism• Discussed one informative study and one
uninformative study in terms of evidence basedmedicine
• Demonstrated that there is no evidenceconnecting vaccines and autism
• Introduced what started the vaccines and autismdebate, and why it continues
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Summary
• Evidence-based Medicine (Leah)• Vaccines (Johnny)• Vaccines and autism, a case study (Alison)
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QUESTIONS?
THANK YOU!