26 April 2009
Concerns About Vaccine Safety
In developed countries where routine childhood immunization has been in place for decades, some diseases have virtually disappeared, and the memories of their fatal or disabling consequences have been forgotten. Most parents in the developed world have never seen a child paralyzed by polio or brain-damaged by measles. As a result, fear of these diseases does not haunt parents as it once did.
At the same time, widely broadcast news stories about pharmaceutical recalls and drug tampering episodes have heightened public concerns about product safety and the reliability of recommendations from the medical establishment. That climate has contributed to resistance among some parents to the regimen of immunizations recommended by government agencies and medical professionals. The Internet has provided a forum in which these fears are further heightened by the rapid transmission of information, which is sometimes misleading or inaccurate.
Many governmental, international, and professional organizations are responding to the concerns about vaccines. The National Network for Immunization Information, for example, offers parents this advice about vaccines.
Vaccine Safety and Risk Perception
No vaccine is 100 percent effective; no vaccine is 100 percent safe. As with any drug, there are risks and side effects with vaccines, although serious side effects are mostly rare. However, there is a much higher standard of safety expected of preventive vaccines than for drugs because:
• Vaccines are generally given to many people, most of whom are healthy. People tolerate far less risk from Haemophilus influenzae type b vaccines than the antibiotics used to treat the diseases it causes, for example.
• Many vaccines are given to children at the ages when developmental and other problems are being recognized for the first time. Because a developmental problem was spotted at about the same time as immunizations were received does not mean that one caused the other.
• Some vaccines are mandated by law in order to protect the health and welfare of the public. Some people think that this violates their civil rights.
Research shows that people respond better to some types of risks than others.
Natural risks (such as infectious diseases) are better tolerated than man-made risks (such as vaccine side effects). Also, risks that affect adults are better tolerated than risks affecting children. Risks that are perceived with unclear benefits may be less tolerated than risks where the benefits are understood.
Take, for example, measles and the MMR (measles-mumps-rubella) vaccine. Since these diseases are no longer epidemic in developed countries, some parents incorrectly assume that the risk of contracting the disease is lower than the risk of their child experiencing an adverse reaction to MMR. They conclude that there may be little benefit from immunizing their child, hence there may seem to be no reason to take the risk of an adverse event. However, there was a mumps outbreak in the United States in 2006, probably introduced from the epidemic in Great Britain. These infections are just a plane ride away.
Perception of risk depends on people’s experiences and knowledge. A person who experienced an adverse event after vaccination—or thinks that they know someone who did—will perceive vaccines as riskier than a person who has not. Conversely, one who has survived a vaccine-preventable disease—or a physician who has treated that disease—will likely be an advocate for vaccines.
Although concerns about vaccine safety are valid and necessary we must carefully examine each claim about the risks of immunizations:
• Is the claim relying on scientific data (for example, large, controlled studies published in respected scientific journals) or on anecdotes (personal stories of sick persons)?
• Are the claims based on facts or are they personal opinions?
Missing Information
When up-to-date, complete, and scientifically valid information about vaccines is available, parents can make informed decisions. Without this information many may develop a false sense of security and regard immunizations as unimportant.
Unfortunately, when a community has low immunization rates, many children, including some who have been immunized, are placed at risk of harm if a highly communicable disease like measles is introduced into the community. With global travel an everyday occurrence, measles may be introduced from another country at any time, posing a threat to communities with low immunization rates. For instance, in March 2004, the U.S. Centers for Disease Control and Prevention (CDC) published information about a student flying from India to Cedar Rapids, Iowa, while incubating measles, as well as cases of measles among children who had recently been adopted from China (see CDC’s report at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm53d319a1.htm).
Like parents, scientists and scientific review groups need data to evaluate vaccine safety concerns. Vaccine safety research often requires very large and often expensive studies that have not been conducted. So when a vaccine safety concern is suggested, the necessary data to support or reject the hypothesis may not yet have been collected—in fact sometimes this may take several years of research. This often leaves scientific review groups like the Institute of Medicine (IOM) Vaccine Safety Committee with insufficient data to be able to fully evaluate vaccine safety concerns.
Another example of missing information arose from a case concerning the hypothesis that the use of thimerosal, a mercury-containing preservative, in vaccines caused autism. This idea was first suggested in 1999, and the ensuing controversy demonstrates the dilemma of insufficient data. In 2001, when the Institute of Medicine’s Immunization Safety Review Committee first examined the issue, it stated that the available evidence was inadequate to decide. In other words, the information was missing. By 2004, however, much more scientific data was available, and the IOM committee was able to conclude that the data favored rejection of a link between vaccines and autism.
Misinformation
Some vaccine safety concerns persist despite the evidence against them. Even when the concern is resolved for most in the scientific community, suspicions about safety may remain an issue for others with vested interests, such as lawyers, journalists, or well-intentioned but misinformed parents.
In spite of the substantial evidence now available that allows rejection of the hypothesis that vaccines cause autism, there are some who continue to state that there is a causal association. These claims, once based on missing information, now fall into the category of misinformation.
Unfortunately, the misinformed person with a fixed opinion about vaccines has many sophisticated tools to disseminate misinformation, creating confusion about vaccine safety. Misinformation comes in many packages and may be widely publicized by the media and others causing lowered immunization levels and heightened disease risk.
Misinformation about vaccines is frequently encountered on the Internet. Some Web sites, for instance, oppose the immunization of infants and children. They express a variety of claims that are largely unsupported by peer-reviewed scientific literature.
Misinformation Web sites tend to ignore or distort scientific studies, instead relying on emotionally filled anecdotes about bad things that happened to children or coincided in time with vaccine administration.
Unfortunately for communities, antivaccination movements have also had a negative effect on public health through the years. One study published in The Lancet in 1998 showed that movements against the whooping cough vaccine caused whooping cough epidemics in several countries.
Adapted by Global Issues with permission, from an article by Martin G. Myers and Diego Pineda (2007) “Vaccine Misinformation”
© National Network for Immunization Information. The original is available at http://www.immunizationinfo.org/immunization_issues_detail.cfv?id=52.
NNii is affiliated with the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, the American Academy of Pediatrics, the American Nurses Association, the American Academy of Family Physicians, the National Association of Pediatric Nurse Practitioners, the American College of Obstetricians and Gynecologists, and the American Medical Association.
The opinions expressed in this article do not necessarily reflect the views or policies of the U.S. government.
From the March 2007 eJournal USA, “Lifesaving Vaccines”
