08.25.11

Autism Not Caused by Vaccines, IOM Report Concludes

Posted in Medication at 4:22 PM by Dr. Greathouse

Autism Not Caused by Vaccines, IOM Report Concludes

By Michael Smith, North American Correspondent, MedPage Today
Published: August 25, 2011
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There’s convincing evidence that some vaccines can cause some adverse effects, including seizures, brain inflammation, and fainting, according to a new report from the Institute of Medicine.

But the evidence also favors rejecting the idea that some vaccines cause type 1 diabetes or autism, the institute said.

The 647-page report was commissioned in 2009 by the Health Resources and Services Administration, which administers the Vaccine Injury Compensation Program. The agency asked the institute to review the evidence linking eight vaccines and a suite of possible adverse effects that have been the subject of compensation claims.

All told, an expert panel convened by the institute found “convincing evidence” that 14 adverse effects can be caused by eight vaccines — those against varicella zoster, influenza, hepatitis B, hepatitis A, human papillomavirus (HPV), measles/mumps/rubella (MMR), and meningococcus, as well as tetanus-containing vaccines that do not carry the whole-cell pertussis component.

Evidence “favors” the idea that vaccines can cause another four adverse effects and favors rejection of the causal link with five others, including autism and diabetes, the expert panel reported.

Finally, evidence is inadequate to accept or reject a causal link in another 135 possible associations.

“The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely,” said the panel’s chair, Ellen Wright Clayton, MD, JD, of Vanderbilt University in Nashville, Tenn.

“And repeated study has made clear that some health problems are not caused by vaccines,” Clayton said in a statement.

The panel established four categories of causation, based on evidence that:

  • “Convincingly supports” a causal relationship, usually on the basis of good epidemiological data and a clear mechanism of action.
  • “Favors acceptance” of a causal relationship, but is not firm enough to be convincing.
  • Is “inadequate to accept or reject” a causal relationship.
  • “Favors rejection” of a causal relationship. Because it’s impossible to prove a negative, the committee did not have a category of evidence that “convincingly” rejects a causal relationship.

The panel was not asked to say how rare potential various adverse effects might be. But, they reported, “many of the adverse events we examined are exceedingly rare in the population overall, and in most instances any particular adverse event, be it arthritis, meningitis, or any of the other vaccine-adverse events that the committee considered, are not preceded by immunization.”

The committee reported convincing evidence that:

  • Because of infection by the vaccine virus strain, the varicella zoster vaccine can cause four specific adverse events — disseminated varicella infection, disseminated varicella infection with subsequent infection resulting in pneumonia, meningitis, or hepatitis in people with immunodeficiencies, vaccine strain viral reactivation, and vaccine strain viral reactivation with subsequent infection resulting in meningitis or encephalitis.
  • The MMR vaccine can cause measles inclusion body encephalitis in people with compromised immune systems.
  • The MMR vaccine also is linked to febrile seizures in infants and young children.
  • Six types of vaccines — MMR, varicella zoster, influenza, hepatitis B, meningococcal, and tetanus-containing vaccines — can cause anaphylaxis.
  • Any of the vaccines can cause syncope and deltoid bursitis.

The experts found evidence “favoring” a causal link between HPV vaccine and anaphylaxis, as well as between the MMR vaccine and transient arthralgia in women and in children.

Also, the committee said, there’s evidence that favors a causal link between some trivalent inactivated influenza vaccines used in Canada recently and a mild and temporary syndrome, characterized by conjunctivitis, facial swelling, and upper respiratory symptoms.

Evidence favored rejection of a causal link in five cases:

  • The MMR vaccine and autism.
  • The MMR vaccine and type 1 diabetes.
  • The tetanus component of the Dtap vaccine and type 1 diabetes.
  • Inactivated influenza vaccine and Bell’s palsy.
  • Inactivated influenza vaccine and exacerbation of asthma or reactive airway disease episodes in children and adults.

The panel cautioned that the “inadequate evidence” category might lead some people to conclude that, “because the committee did not find convincing evidence that the vaccine does cause the adverse event, the vaccine is safe.”

Others, they said, might take the opposite tack: because the committee did not find convincing evidence that the vaccine does not cause the adverse event, the vaccine is unsafe.

“Neither of these interpretations is correct,” the report concludes. “‘Inadequate to accept or reject’ means just that – inadequate.”

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