Childhood Immunizations and Autism

Childhood Immunizations and Autism:
Factual or Fanatical?

Chad Cox

Penn State University College of Medicine

2003

MMR Vaccine

• Ü Combination vaccine used to protect children from mumps, measles and rubella (German measles)
• Ü First dose of the vaccine is usually given to children 12 to 15 months old
• Ü Second dose is usually given between 4 and 6 years of age

Vaccination side effects

• Ü Most people who receive vaccines experience no, or only mild, reactions such as fever or soreness at the injection site
• Ü Very rarely, people experience more serious side effects, like allergic reactions

Vaccination side effects

• Ü Rare Side Effects
• – Severe allergic reactions (Low probability in all vaccines)
• – Guillain-Barré Syndrome (influenza)
• – Deafness (MMR)
• – Seizures, coma or lowered consciousness (MMR)
• – Permanent brain damage (MMR)
• – Pneumonia (varicella)
• – Muscle wasting (Tetanus and Pertussis)

MMR and autism

• Ü Wakefield and colleagues first reported a possible association between the MMR vaccine and a syndrome of autistic regression in The Lancet 1998(Feb 28);351:637-641
• Ü Subjects
• Ü 12 children, referred consecutively to the Dept of Pediatric Gastroenterology with a history of Pervasive Developmental Disorder (9 with diagnosis of autism) and loss of acquired skills and intestinal symptoms.

MMR and autism

• Ü Onset of behavioral symptoms was associated by the parents with MMR vaccination in eight of the 12 children

MMR and autism

• Ü Weaknesses
• – Too few cases (12 children)
• – No healthy controls for comparison
• – No reported time period during which cases were identified
• Ü In their discussion, they state, “We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described.“

DSM IV criteria for Autism

• Ü Qualitative impairment in social interaction and communication
• Ü Restricted repetitive and stereotyped patterns of behavior, interests and activities
• Ü Delays or abnormal functioning in social interaction, language or imaginative play with onset before age 3
• Ü Reported to be increasing in incidence from 1 in approximately 2500 in the mid-1980s to 1 in approximately 300 children in the mid-1990s

MMR and autism

• Ü Since the Wakefield study was published in 1998, a number of other studies have also been published that suggest a link between the MMR vaccine and autism
• – Singh et al 1998
• – Horvath et al 1999
• – O’Leary et al 2000
• – Wakefield et al 2000
• – Kawashima et al 2000

MMR and autism

• Ü However, the vast majority of studies have shown no association.
• – National Childhood Encephalopathy Study 1999
• – Gillberg and Heijbel 1998
• – British Committee on Safety of Medicines “Working Party on MMR Vaccine” 1999
• – Taylor et al (UK) 1999
• – Kaye et al (UK) 2001
• – Dales et al. (California) 2001
• – Frombonne & Chakrabarti (UK) 2001
• – Taylor et al. (UK) 2002
• – Madsen et al. (Denmark) 2002

Institute of Medicine Report, 2001

• Ü In 2000, the Institute of Medicine (IOM), at the request of the Centers for Disease Control and Prevention (CDC) and the NIH, conducted a review of all the evidence related to the MMR vaccine and autism. This independent panel examined completed studies, on-going studies, published medical and scientific papers, and expert testimony to assess whether or not there was a link between autism and the MMR vaccine. The IOM concluded that the evidence reviewed did not support an association between autism and the MMR vaccine. This and other conclusions from the IOM review were released in April 2001 (Immunization Safety Review Committee 2001).

Institute of Medicine Report 2001

• Ü The majority of cases of autism cannot be caused by MMR vaccine
• Ü MMR cannot explain the recent increasing trends in autism diagnoses
• Ü information is insufficient to totally exclude MMR as a cause of autism in rare instances
• Ü No epidemiologic study or clinical trial can ever establish that a vaccine is absolutely safe or that a particular vaccine reaction never occurs

Case closed………or reopened?

• Ü Recent article by Geier and Geier (Pediatr Rehabil. 2003 Apr-Jun;6(2):97-102) suggests a link between vaccines containing Thimerosal and autism
• Ü Study was poorly done. However, results have revitalized vaccine-autism debate.

Thimerosal

• Ü Thimerosal is used as a preservative in some multi-dose vials of vaccines to prevent contamination
• – HepB DTP
• – influenza pneumo
• – Rabies Not in MMR vaccine
• Ü No harmful effects described except for minor local reactions (Ball et al., 2001).
• Ü However, in July 1999 the Public Health Service agencies (PHS), the American Academy of Pediatrics (AAP), and vaccine manufacturers agreed to reduce thimerosal as a precaution

Thimerosal and autism

• Ü The vast majority of studies have found no link between vaccines containing thimerosal and autism
• – Stehr-Green et al 2002
• – Madsen et al 2003 (Denmark)
• – Stokstad 2003
• – Hviid et al Oct 2003 (Denmark)
• – Verstraeten et al Nov 2003

Conclusion

• Ü No study has conclusively shown that the MMR vaccine causes autism. On the contrary, the majority of studies, including the large-scale study performed by the Institute of Medicine, have shown no association.
• Ü There has been no consistent association found between use of thimerosal in childhood vaccinations and autism. However, as a precautionary measure, use of thimerosal in vaccine preparations is decreasing.
• Ü Regardless of what the science says, this issue will continue to be debated for years to come.