Vaccine side effects rare, review finds
Vaccines rarely cause serious side effects, according to a new, comprehensive scientific review, and when problems do arise, they are mostly in people with pre-existing immune system disorders.
The report, put together by an independent panel of medical experts convened by the Institute of Medicine, will be used to help administer claims through the Vaccine Injury Compensation Program, which was established in 1986 to provide financial redress to people who are harmed by eight recommended vaccines.
Vaccine safety is a highly charged issue. Fears that vaccines can cause various side effects have led to a decline in childhood immunization rates in recent years and a re-emergence of preventable infectious diseases such as pertussis and measles.
“The utility of this report is enormous,” said Dr. Ellen Wright Clayton, the committee chairwoman and director of the Center for Biomedical Ethics and Society at Vanderbilt University in Nashville. “Claimants and the government and the vaccine court will now have available to them the best analysis that has ever been done about the potential adverse events caused by these vaccines.”
The committee reviewed more than 1,000 scientific articles in assessing vaccine safety for the report, which was released Thursday. The first comprehensive review of the issue by the IOM since 1994, it supports several previously published studies that failed to find a link between the measles-mumps-rubella (MMR) vaccine and autism.
Moreover, the panel said it could find no evidence to support claims by some parents that the diphtheria-tetanus-acellular pertussis vaccine causes Type 1 diabetes or that the flu shot worsens asthma or causes Bell’s palsy, a nerve disorder that results in temporary paralysis of the muscles in the face.
The report did find evidence that various vaccines can produce a range of side effects, usually minor, such as fainting or soreness at the injection site.
And it found clear evidence that six vaccines – the MMR vaccine as well as ones protecting against influenza, varicella (chickenpox), hepatitis B, meningococcal disease and tetanus – can cause anaphylaxis, a sudden, life-threatening allergic reaction. The varicella vaccine was linked to rare cases of infection in people with immune-system disorders as well as some people with healthy immune systems.
However, the panel said there is not enough scientific evidence to accept or reject a relationship between influenza vaccine and rare cases of Guillain-Barre syndrome, in which parts of the nervous system are attacked by the immune system, leading to body weakness or even paralysis.
And it did not answer one of the most pressing current questions regarding vaccine safety. Gardasil, a vaccine to protect against common strains of human papillomavirus that can cause cervical cancer, has been associated with isolated cases of blood clots and even some deaths. But the report says there is not enough scientific evidence yet to determine whether HPV vaccines, available since 2006, are responsible.
“We did not find studies that were sound enough to consider to make any kind of judgment on that association,” said Dr. S. Claiborne Johnston, a committee member and professor of neurology and epidemiology at UC San Francisco.
But, Clayton added, the HPV vaccine data that exist revealed “nothing that was alarming, so far.”
Not everyone reviewing the report is convinced by its findings. The document shows that there is not enough scientific evidence to guarantee the safety of certain vaccines, said Barbara Loe Fisher, co-founder and president of the National Vaccine Information Center, a nonprofit organization in Vienna, Va., that has lobbied for more information on vaccine safety and parental choice about vaccinating their children.
“In the majority of cases when they looked at the scientific literature, there was inadequate evidence for them to accept or reject causation” of adverse events, she said. “I think that points out the urgent need for more high-quality vaccine safety science.”
Clayton said vaccines are to be credited with a dramatic plunge in several infectious diseases over the past half-century.
“We have a lot of evidence that vaccines save lives and avert a lot of suffering,” she said.
Yet health experts are worried by recent trends. A report released last year by the nonprofit National Committee for Quality Assurance found that vaccination rates among toddlers covered by private health insurance plans fell almost 4 percent in 2009, and health experts speculate that much of the decline is due to fears over safety – especially the belief that vaccines are linked to autism.
The report should help pediatricians and family practitioners allay parents’ concerns over vaccine safety, Johnston said.