Current Opinion from IOM on Autism and Vaccination

Some parents and families of children with autism believe that the Measles/Mumps/ Rubella (MMR) vaccine caused their children’s autism. These parents report that their children were “normal” until they received the MMR vaccine. Then, after getting the vaccine, their children started showing symptoms of autism. Because the symptoms of autism (an increasingly common neurodevelopmental problem) begin to occur around the same time as the child’s MMR vaccination, parents and families see the vaccine as the cause of the autism. However, just because the events happen around the same time does not mean that one caused the other. Although children receive many other vaccines in addition to the MMR vaccine, these other vaccines have not been identified as possible causes of autism.

This has remained and despite the IOM findings below will probably continue to remain a highly emotive area, with neither side finding complete satisfaction in outcome.

Adverse Effects of Vaccines: Evidence and Causality a consensus report published August 25^th 2011.[1]

So what do the Institute of Medicine (IOM) findings primarily describe:

They agree: There’s convincing evidence that some vaccines can cause some adverse effects, including seizures, brain inflammation, and fainting. But their 600 pages plus paper also favours rejecting the idea that some vaccines cause type 1 diabetes or autism.

The 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.

The expert panel chaired by Ellen Wright Clayton, MD, JD, of Vanderbilt University in Nashville, Tennessee 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.

They stated that evidence “favours” the idea that vaccines can cause another four adverse effects and favors rejection of the causal link with five others, including autism and diabetes.

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

Categories of causation

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.
• “Favours acceptance” of a causal relationship, but is not firm enough to be convincing.
• Is “inadequate to accept or reject” a causal relationship.
• “Favours 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 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 (fainting) and deltoid bursitis.

The experts found evidence “favouring” 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 favours a causal link between some trivalent inactivated influenza vaccines used in Canada recently and a mild and temporary syndrome, characterised by conjunctivitis, facial swelling, and upper respiratory symptoms.

Evidence favoured 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.

Comments

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.”

What do you think?

Reference

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[1] Adverse Effects of Vaccines: Evidence and Causality a consensus report published august 25^th 2011. View Report