IOM Report: Vaccines Are Largely Safe

An extensive review of more than 1,000 research articles concluded that few health problems are caused by or clearly associated with vaccines.

A committee of experts convened by the Institute of Medicine to review the scientific literature on possible adverse effects of vaccines found convincing evidence of 14 health outcomes—including seizures, inflammation of the brain, and fainting—that can be caused by certain vaccines, although these outcomes occur rarely. The report, which was issued by the Institute of Medicine, found no links between immunization and a number of serious conditions that have raised concerns, including Type 1 diabetes and autism.

Suggestions that vaccines can lead to these health problems have contributed to parental concerns about immunization for their children.

"With the start of the new school year, it's time to ensure that children are up to date on their immunizations, making this report's findings about the safety of these eight vaccines particularly timely," said committee chair Ellen Wright Clayton, JD, MD, of Vanderbilt University, in a statement.

The review was commissioned by the US Department of Health and Human Services to help administer the Vaccine Injury Compensation Program, which provides funds to care for children who experience adverse effects from vaccines.

Convincing evidence shows that the measles-mumps-rubella (MMR) vaccine can lead to fever-triggered seizures in some individuals, although these effects are almost always without long-term consequences, the report stated. The MMR vaccine also can produce a rare form of brain inflammation in some people with severe immune system deficiencies.

In a minority of patients, the varicella vaccine against chickenpox can induce brain swelling, pneumonia, hepatitis, meningitis, shingles, and chickenpox in immunocompromised patients as well as some who apparently have competent immune function, the committee found. The majority of these problems have occurred in individuals with immunodeficiencies, which increase individuals' susceptibility to the live viruses used in MMR and varicella.

Six vaccines—MMR, varicella, influenza, hepatitis B, meningococcal, and the tetanus-containing vaccines—can trigger anaphylaxis. And in general, the injection of vaccines can trigger fainting and inflammation of the shoulder, the committee noted.

The evidence suggests that certain vaccines can lead to 4 other adverse effects, although the data on these links are not as convincing, the report stated.

• The MMR vaccine appears to trigger short-term joint pain in some women and children.
• Some people can experience anaphylaxis after receiving the HPV vaccine.
• Certain influenza vaccines used abroad have resulted in a mild, temporary oculo-respiratory syndrome characterized by conjunctivitis, facial swelling, and mild respiratory symptoms.

The review also concluded that certain vaccines are not linked to 4 specific conditions. The MMR vaccine and diphtheria-tetanus-acellular pertussis (DTaP) do not cause Type 1 diabetes, and the MMR vaccine does not cause autism, according to the results of several studies. The evidence shows that the flu shot does not cause Bell's palsy or exacerbate asthma.

"The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely,” said Dr. Clayton. “And repeated study has made clear that some health problems are not caused by vaccines."

To access the report, click here.

For more:

• Removing Barriers to Childhood Immunization
• Vaccinations: The Expanding Role of Pharmacists
• Beyond Genes: Looking at What Causes Autism