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IOM: Serious Adverse Events Rare With Vaccines
Extensive Review Finds Few Causal Relationships
Campos-Outcalt said the report is an excellent source of information for family physicians. Although he acknowledged that the 667-page report is "not good bedtime reading" for the average patient, a free six-page report brief (6-page PDF; About PDFs) is available. The IOM also has released a one-page table (1-page PDF; About PDFs) that summarizes the level of evidence related to a potential adverse event and a specific vaccine.
- The Institute of Medicine, or IOM, has released a review of evidence regarding vaccines and adverse events.
- The IOM committee found that evidence refuted purported links between the measles, mumps and rubella vaccine and both autism and type 1 diabetes.
- The committee also found that most serious adverse events were rare and often involved patients with compromised immune systems.
The Health Resources and Services Administration, the HHS agency that administers the National Vaccine Injury Compensation Program, requested the review. It marks the third time the IOM has reviewed adverse events since the compensation program was created by Congress in 1986 and the first time since 1994.
Committee chair Ellen Wright Clayton, M.D., J.D., professor of pediatrics and law, and director of the Center for Biomedical Ethics and Society at Vanderbilt University, called the report "the best analysis that's ever been done about potential adverse events" during an Aug. 25 media briefing.
"We have a lot of evidence that vaccines save lives and avert a lot of suffering," she said. "The side effects that we're talking about are relatively rare because it's hard to find them in the general population. The majority of them are short term or readily treated."
An IOM committee reviewed adverse event reports related to vaccines for hepatitis A; hepatitis B; human papillomavirus, or HPV; influenza; measles, mumps and rubella, or MMR; meningococcal disease; tetanus; and varicella. Based on the evidence, the committee assigned 158 vaccine and adverse event relationships to one of the following categories:
- evidence convincingly supports causal relationship;
- evidence favors acceptance of causal relationship;
- evidence favors rejection of causal relationship; and
- evidence is inadequate to accept or reject causal relationship.
The committee said evidence favored rejection of five vaccine and adverse event relationships:
- MMR vaccine and autism;
- MMR vaccine and type 1 diabetes;
- diphtheria and tetanus toxoids and acellular pertussis, or DTaP, vaccine and type 1 diabetes;
- inactivated influenza vaccine and Bell's palsy; and
- inactivated influenza vaccine and exacerbation of asthma or reactive airway disease episodes in children and adults.
The CDC said Sept. 2 that there have been 198 cases and 15 confirmed outbreaks of measles this year in the United States, the highest number since 1996. Ninety percent of the cases were associated with U.S. residents traveling internationally.
The IOM committee, however, did find convincing evidence of a casual relationship between MMR and other side effects, including measles inclusion body encephalitis, which in rare cases can affect people with compromised immune systems, and febrile seizures.
MMR also was one of six types of vaccines -- the others were varicella zoster, influenza, hepatitis B, meningococcal, and tetanus-containing vaccines -- linked to anaphylaxis.
Several other vaccines and adverse events also fell into the category that found convincing evidence to support causal relationships. For example, varicella zoster vaccine is linked to four adverse events due to infection from the vaccine virus strain, including disseminated varicella infection shortly after vaccination and disseminated varicella infection with subsequent infection resulting in pneumonia, meningitis or hepatitis in individuals with immunodeficiencies.
The committee also found convincing evidence of a causal relationship between injection of vaccines, regardless of the antigen involved, and syncope and deltoid bursitis.
Four vaccine and adverse event relationships fell into the category of having evidence that favors acceptance of a causal relationship, which means the committee found strong, but not convincing, evidence:
- HPV vaccine and anaphylaxis;
- MMR vaccine and transient arthralgia in female adults;
- MMR vaccine and transient arthralgia in children; and
- certain trivalent inactivated influenza vaccines used in Canada in some recent years and a mild and temporary oculorespiratory syndrome, which is characterized by conjunctivitis, facial swelling and upper respiratory symptoms.