Vaccine analysis further debunks autism and diabetes links

The measles, mumps and rubella vaccine does not cause autism or type 1 diabetes, says an Institute of Medicine committee that examined potential side effects of certain vaccines recommended by the Centers for Disease Control and Prevention.

In the IOM's first comprehensive review of vaccine safety in 17 years, experts found that few health problems are caused by immunizations. When side effects occur, the medical conditions often are short term or easily treated.

"All health care interventions carry the possibility of risk, and vaccines are not an exception," said Ellen Wright Clayton, MD, chair of the IOM's Committee to Review Adverse Effects of Vaccines. She is a professor of pediatrics at Vanderbilt University School of Medicine in Nashville, Tenn.

"We have a lot of evidence that vaccines save lives and avert a lot of suffering," she said. "The side effects we're talking about here are relatively rare ... and are either short-term or are readily treated. That would be the take-home message."

The 16-member committee, which included pediatricians, internists and immunologists, assessed more than 1,000 studies issued between April 2009 and March 2011. The federal government requested the examination, asking the committee to review evidence regarding adverse health events associated with some vaccines that are covered by the National Vaccine Injury Compensation Program. The program provides financial compensation for people, usually children, who can prove that an injury or illness is caused by an immunization.

The IOM report, issued Aug. 25, is expected to help the Dept. of Health and Human Services guide compensation decisions.

The report also will be a useful tool for physicians, particularly pediatricians, who often have to address parents' worries about vaccine safety, Dr. Clayton said.

"I am hopeful [the findings] will allay some people's concerns," she said.

Experts examined studies on the following immunizations: hepatitis A, hepatitis B, human papillomavirus, meningococcal, MMR, seasonal influenza, varicella and tetanus-containing vaccines that do not carry the whole-cell pertussis component.

Committee members found convincing evidence of 14 side effects that can be caused by the studied immunizations. Included in this category is the MMR vaccine, which can cause measles inclusion body encephalitis in immunocompromised people and febrile seizures. The seizures usually are benign and have no long-term consequences, the committee said.

In a minority of patients, the varicella vaccine can induce brain swelling, pneumonia, hepatitis, meningitis, shingles and chickenpox. Anaphylaxis can be triggered by six immunizations shortly after injection: hepatitis B, influenza, meningococcal, MMR, varicella and the tetanus containing vaccines. In general, the injection of immunizations can cause fainting and deltoid bursitis.

Putting the findings in perspective, committee member S. Claiborne Johnston, MD, PhD, said the most serious side effects, such as brain inflammation caused by the MMR vaccine, were identified only in case reports, not in epidemiological studies. This indicates that the adverse event rarely occurs, he said.

"We're talking about millions of vaccines [administered] and only a few case reports of those events," said Dr. Johnston, director of the Neurovascular Disease and Stroke Center at the University of California, San Francisco Medical Center.

The validity of vaccines

Evidence suggests that certain vaccines can lead to other adverse effects, but the data on these links are not as convincing, the committee said.

The incidents include short-term joint pain in some children and women after receiving the MMR vaccine.

People can experience anaphylaxis after getting the HPV immunization. And certain influenza vaccines administered in Canada have resulted in a mild, temporary oculorespiratory syndrome characterized by conjunctivitis, facial swelling and mild respiratory symptoms.

Additionally, the committee determined that the DTaP vaccine does not cause type 1 diabetes, and the influenza immunization does not lead to Bell's palsy or exacerbate asthma.

"Can [certain] vaccines cause an adverse event in some people? Yes. But that doesn't reduce the validity of some vaccines to reduce illness and morbidity" in individuals, said Douglas J. Barrett, MD, a professor in the department of pediatrics and immunology at the University of Florida College of Medicine in Gainesville.