Immunization Issues

Vaccine Misinformation

Updated: February 12, 2009

Decades ago, when thousands of children and adults in the United States contracted smallpox, diphtheria, poliomyelitis or measles each year, vaccine safety concerns were not very common. People were more afraid of the diseases themselves than of possible side effects of the vaccines.

Today the situation is different; because of vaccines most parents have not encountered these once-dreaded diseases. For instance:

Most parents today have not seen a child paralyzed by polio, or choking to death from diphtheria, or brain damaged by measles. Fear of vaccine-preventable diseases has diminished while concerns about vaccine safety have increased—even though a number of the vaccines are even safer than decades ago as a result of medical research.

A lack of information or erroneous information about vaccine safety and effectiveness can create confusion among parents who are considering immunizations for their children; this can have tragic consequences.

For instance, pertussis outbreaks in England and Wales, Japan, and Sweden have been attributed to misinformation about pertussis vaccine safety in the late 1970s and 1980s. Measles and mumps outbreaks in many countries followed misinformation about measles vaccine as a cause of autism in the UK.1 And in 2008 three unimmunized children in Minnesota developed invasive disease due to Haemophilus influenzae, type B (Hib) infection. One of the children died. Two other children who also developed invasive Hib disease should have been protected by community immunity, but were not.2

Vaccine safety concerns and risk perception 

No vaccine is 100% effective; no vaccine is 100% 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 something happened at about the same time does not mean that one caused the other.  (See Cause or Coincidence)
  • Some vaccines are mandated by state legislatures in order to protect the health and welfare of the public. Some people think that this violates their civil rights, however.

Research shows that people respond better to some types of risks than others.

Natural risks (such as infectious diseases) are better tolerated than manmade risks (such as vaccine side effects). Also, risks that affect adults are better tolerated than risks affecting our 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 the United States, 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. Most of the 173 cases of measles in the United States in 2008 occurred among unimmunized children; measles introductions that year were largely from Europe. 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? 
  • See Evaluating Information on the Web for more questions and answers on this topic.

Missing information

When up-to-date, complete, and scientifically valid information about vaccines is available, parents can make informed decisions. For example, they need to have access to accurate evidence-based information so that they understand the risks of exposure parties, the importance of community immunity, and what the actual risks of complications are (see Vaccine Information). Without this information many may develop a false sense of security and regard immunizations as unimportant.

For example, measles is the most communicable of diseases, has many serious complications and can cause severe brain damage or be fatal. But when a vaccine-preventable disease such as measles is no longer common in a community, parents may not see the need to vaccinate their children against measles, resulting in low immunization rates.

Unfortunately, when a community has low immunization rates, many children—including some who have been immunized—are placed at risk of harm if measles is introduced into the community. With global travel an everyday occurrence, measles is just a plane ride away. For instance, in March 2004, the CDC published information about a student flying from India to Cedar Rapids, Iowa, while incubating measles3

Like parents, scientists and scientific review groups need data to evaluate vaccine safety concerns. Vaccine safety research often requires very large—often expensive—studies that do not compete well with other types of research funded by the Federal government.

Unfortunately, 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 Vaccine Safety Committee with insufficient data to be able to fully evaluate vaccine safety concerns.

The experience concerning the hypothesis that thimerosal in vaccines caused autism—first suggested in 1999—is illustrative of the dilemma of insufficient data (missing information). In 2001, when the Institute of Medicine’s Immunization Safety Review Committee first examined the issue, it stated that at that time the available evidence was inadequate to decide.4 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 that hypothesis.5

Misinformation (false or misleading information) 

The timing and widespread use of vaccines make them easy scapegoats to be blamed for all sorts of serious illnesses. Of course not all vaccine safety concerns are misinformation—only those that persist despite the evidence against them. Even when the concern stops being an issue for most in the scientific community, it may remain an issue for many others with vested interests—whether politicians, lawyers, journalists or the group that concerns health professionals the most: well intentioned but misinformed parents trying to understand and alleviate their child’s afflictions. Many media stories use faulty reports and parental concerns to depict a “controversy” about vaccines, failing to mention that the scientific community does not feel that a controversy exists.

In spite of the substantial evidence now available that allows rejection of the hypotheses 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 disease risk.

For example, a misinformed couple in Tennessee, confused about vaccine safety because of what they had read on the Internet, decided to delay their daughter’s vaccinations. Some time later, the baby girl was stricken with a form of meningitis that could have been prevented by a vaccine.6

Misinformation also involves the intentional dissemination of false information. In this case, people are not only confused about vaccine safety but may be against vaccines altogether.

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 (See table below).

Misinformation Web sites tend to rely on emotionally-filled anecdotes about bad things that happened to children or were first recognized—coincidental in time with vaccine administration—while ignoring or distorting scientific studies.7

Unfortunately for communities, antivaccination movements have also had a negative effect on public health through the years. One study, for example, showed that movements against the whooping cough vaccine caused whooping cough epidemics in several countries.8

How can you distinguish good information from misinformation? Misinformation often includes one or more of the following elements:

  • Invalid assumptions. An invalid assumption is something you treat as if it were known to be true or false, when in fact it is not. For example, some parents regard hepatitis B immunization as unnecessary, assuming that this is a disease for which their children are not at risk. This is an invalid assumption (read here to know why).
  • Logical Fallacies. A logical fallacy is a flaw in an argument that makes the argument illogic or invalid. Some common logical fallacies are ad hominem arguments (attacking those presenting the argument rather than the argument itself); appeals to pity (trying to win support for one’s arguments by appealing to feelings of sympathy or guilt); and arguments from ignorance (claiming that a statement is true only because it has not been proven false, or that it is false only because it has not been proven true) among others.
  • Ad hoc hypotheses. An ad hoc (literally, “for this”) hypothesis is an adjustment made to a theory just for the purpose of salvaging it from being refuted. Ad hoc explanations try to explain findings that do not fit the original theory.
  • False experts or experts who lack the needed expertise. An expert in one field may be completely ignorant in another field. For instance, an expert endocrinologist may be an expert on diabetes but is not likely to be expert about vaccine safety or immunology. Unfortunately, some who may be experts in one field eagerly make claims about things outside their field of expertise.
  • Pseudoscience. Pseudoscientific claims cannot be verified by other researchers because they are often ambiguous and not measurable. In most cases, these claims are not submitted to peer review (that is, review by experts) before making them public and the methods are usually difficult to understand, making the observations difficult to replicate. Often, data may be represented to show one outcome when another is the case. Other times the methods that are used are likely to give a predetermined outcome. Only data purporting to support the claims is presented while conflicting data are ignored or discarded.

Common claims found on misinformationWeb sites



Natural methods of enhancing immunity are better than vaccinations.

The only ‘natural way’ to be immune is to have the disease. Immunity from a preventive vaccine provides protection against disease when a person is exposed to it in the future. That immunity is usually similar to what is acquired from natural infection, although several doses of a vaccine may have to be given for a child to have a full immune response.

Epidemiology—often used to establish vaccine safety—is not science but number crunching.

Epidemiology is a well-established scientific discipline that, among other things, identifies the cause of diseases and the factors that increase a person’s risk for a disease.

Giving multiple vaccines at the same time causes an ‘overload’ of the immune system.

Vaccination does not overburden a child’s immune system; the recommended vaccines use only a small portion of the immune system’s “memory”.

Vaccines are ineffective.

Vaccines have spared millions of people the effects of devastating diseases. (See Vaccine effectiveness).

Prior to the use of vaccinations these diseases had begun to decline due to improved nutrition and hygiene.

In the 19th and 20th centuries, some infectious diseases began to be better controlled because of improvements in sanitation, clean water, pasteurized milk, pest control, etc. However, vaccine-preventable diseases only began to drop dramatically after the vaccines for those diseases were licensed and were given to large numbers of children. (See Vaccine effectiveness).

Vaccines cause illnesses or disorders of unknown cause such as autism, sudden infant death syndrome (SIDS), immune dysfunction, diabetes, neurological disorders, allergic rhinitis, eczema, and asthma.

Scientific evidence does not support these claims. See IOM reports.

Contaminated vaccination lots (or “hot lots”) are more likely to cause an adverse reaction.

The Food and Drug Administration regulates the production of vaccines very carefully to assure the potency, purity and safety of vaccines.