MMR Vaccine Does Not Cause Autism, Says IOM

An Institute of Medicine committee has found convincing evidence that some common vaccines – varicella zoster; measles, mumps and rubella (MMR); influenza, hepatitis B, meningococcal and tetanus – may in rare cases cause 14 adverse health effects, according to an influential report released Thursday.

However, the 667-page report said the 16-member committee found no or insufficient evidence to link the MMR vaccine with autism or type I diabetes, nor did it connect the tetanus vaccine with type I diabetes, or the inactivated influenza vaccine with Bell's palsy or exacerbation of asthma or reactive airway disease. The committee reviewed more than 1,000 research articles to draw its conclusions.

"The MMR vaccine does not cause autism, and the MMR and the DPT or diphtheria, tetanus, pertussis vaccines do not cause type I diabetes and killed flu vaccine or the flu shot does not cause Bell's palsy and does not trigger episodes of asthma," Ellen Wright Clayton, M.D., director of the Center for Biomedical Ethics and Society at Vanderbilt University in Nashville, said in a news briefing to release the report.

"It is important to note that just because something bad happened after getting a vaccine, or a drug for that matter, it does not mean that the vaccine or drug actually caused that. It could have been just a coincidence or it could be that the health problem was caused by something else," she said.

The committee placed vaccines into one of four categories: evidence convincingly supports a causal relationship, evidence favors acceptance of a causal relationship but is not firm enough to be convincing, evidence favors rejection of a causal relationship and evidence is inadequate to accept or reject a causal relationship.

During the briefing, several committee members stressed that vaccination side-effects are far less risky than the harm that could be caused by the diseases they prevent.

"People forget what these diseases are like," Wright-Clayton added, giving examples of cases of tetanus and Haemophilus influenza she treated as a resident physician. "They are very bad diseases."

However, the committee determined that there is convincing evidence to support a causal relationship (the first category) between the varicella zoster vaccine to four specific adverse events, all due to infection from the vaccine virus strain, and placed this vaccine in the first category.

The adverse events that there is convincing evidence are linked to these vaccines include disseminated varicella infection, a widespread chickenpox rash shortly after vaccination, varicella infection with subsequent infection resulting in pneumonia, meningitis or hepatitis in people with immunodeficiencies, vaccine strain viral reactivation – manifested as the appearance of chickenpox rash months to years after vaccination – and vaccine strain viral reactivation with subsequent infection resulting in meningitis or encephalitis, or inflammation of the brain.

Also in the first category is the MMR vaccine, which the committee linked to a disease called "measles inclusion body encephalitis," in which rare cases affect people whose immune systems are compromised usually within a year of acute measles infection or vaccination.

Six types of vaccines, including MMR, varicella zoster, influenza, hepatitis B, meningococcal and tetanus, were linked to anaphylaxis.

Last in the first category, the committee found convincing evidence of a causal relationship between injection of a vaccine and two types of adverse events – syncope or fainting and deltoid bursitis or frozen shoulder.

Some vaccines were placed in the third category, in which the evidence was strong and generally suggestive that a causal relationship exists, but is "not firm enough to be described as convincing," the report said. 

These vaccines and side effects include human papillomavirus vaccine and anaphylaxis, MMR and transient arthralgia or temporary joint pain in female adults and in children, and certain trivalent inactivated influenza vaccines used in Canada in recent years and a mild, temporary oculorespiratory syndrome characterized by conjunctivitis, facial swelling, coughing and wheezing.

The committee put 135 other vaccine and adverse event pairs into the fourth category, in which the evidence was "inadequate to accept or reject a causal relationship. Those included extremely rare conditions that were hard to study,

This is the IOM's third report on the topic of vaccines and human side-effects, but the first since 1994. It was requested by the Health Resources and Services Administration to help determine justification for claims filed with the National Vaccine Injury Compensation Program, which determines financial payments to people who were injured by vaccines. Eight of the 12 covered vaccines were requested for review.

The committee members said they were not asked to describe the frequency with which these rare events occur and did not do so in response to questions.

Claiborne Johnston, MD, a member of the committee and director of the Neurovascular Disease and Stroke Center at the University of Califorina San Francisco, acknowledged that the committee did not quantify the number of adverse events likely to stem from administration of any of these vaccines.

"You think about an apple. Can an apple cause choking?" he asked. "Our task was to determine whether an apple could cause choking, it was not to say how frequently does choking occur or to ask whether the benefits of an apple are outweighed by the rarity of choking."

However, he added, "if you look at the safety issues that we did identify, where there was significant evidence you have some serious adverse events associated with these vaccines, particularly the live vaccines, those are rare, and almost always the vaccines are preventing more of the event that they're causing. So it looks like the net benefit for any given parent or kid is clearly positive."

Many adverse events are time-limited, such as fainting, and very controllable, he said.

He said committee members expect that the report will be more useful to clinicians than the public, and that providers "will use it to inform parents about vaccinating their kids."

See Also:
HHS Updates National Vaccine Plan
Healthcare Workers Still Skeptical About Flu Vaccinations