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Am Fam Physician. 2003;67(3):651-656

Case Scenario

Some of my young patients have parents who, despite being well educated have, in my opinion, some irrational beliefs. An example of this is a young mother who recently refused to vaccinate her baby. This mother said that she had heard of adverse reactions to vaccines, and she did not want to risk her baby's health. She had heard that some vaccines have dangerous additives, that the measles vaccine is associated with autism, and that the varicella vaccine could cause her child to have chickenpox in adulthood when it would be more dangerous. Vaccines, she had read, weaken the immune system.

I tried to explain that many of her concerns have been addressed or repudiated, but she would have none of it. “Doctors are uninformed about the risks of vaccines,” she said. “Vaccines actually cause diseases instead of preventing them.” This seemed like too much of an argument for me to tackle during an office visit.

I concluded that this mother is taking advantage of the fact that other children are immunized and relies on the immunization of others to protect her child from diseases. I suggested that she think about the benefits of immunizations and remain open to changing her mind.


Physicians may find it incredible that some parents are reluctant to immunize their children despite the tremendous successes of vaccines in decreasing the morbidity and mortality of childhood diseases. Unfortunately, this particular scenario is likely to become more common because parents no longer see these diseases; they focus instead on the rare but often sensationalized adverse effects of vaccines. The accompanying table summarizes a variety of factors that may affect a person's perception of vaccine risks. In particular, parents may overestimate the frequency of serious vaccine risks or avoid doing anything that might put their child at risk, even if the risk is much less than the child could encounter from the disease itself.1 Parents also may have the idea that their child is protected because other children have been immunized.

Physicians should acknowledge that vaccines are not always 100 percent effective and, in rare instances, can have serious adverse effects. However, it also should be pointed out that the benefits of immunization almost always exceed the potential risks. For example, measles kills almost 1 million children worldwide each year, especially in developing countries. From 1989 to 1991, more than 55,000 children in the United States contracted measles, and more than 120 of them died.2 After a campaign to improve immunization rates with the measles, mumps, and rubella (MMR) vaccine, the annual number of reported measles cases in the United States is now less than 100. A significant percentage of U.S. measles cases, however, are imported from other countries.

In 1999, the U.S. Food and Drug Administration determined that the use of the mercury-containing preservative thimerosal in vaccines might, theoretically, expose infants to more mercury than is recommended. Except for local hypersensitivity reactions, thimerosal has not been found to cause any harm.3 Even so, the preservative has been removed from all routine childhood vaccines that previously contained it.

Allegations also have been made of a link between autism and the MMR vaccine. In 1998, Wakefield and colleagues4 reviewed 12 children with ileal-lymphoid-nodular hyperplasia, nonspecific colitis, and pervasive developmental disorder. Although parents associated the onset of behavior symptoms with MMR vaccination in eight of the 12 children (who did not have preceding bowel symptoms), the investigators noted that “We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described.”4

Voluntary controllable risksMore acceptable than involuntary risks
Natural risksMore acceptable than man-made risks
Frightening or memorable risksLess acceptable than less frightening or less memorable risks
Risks due to commission (action)Less acceptable than risks due to omission (i.e., not vaccinating) bias
Ambiguity aversionKnown risks may be more acceptable than unknown risks of lesser magnitude (e.g., risks of disease vs. new vaccine)
FreeloadingRely on high vaccination rate and herd immunity to protect unvaccinated
BandwagoningVaccinate because everyone else is
AltruismAccept personal risk to benefit community or society

A much larger study5 of 498 autistic children in the United Kingdom did not confirm a causal association between MMR vaccine and autism. The U.S. Institute of Medicine concluded that current evidence favored rejection of a causal relationship at the population level between MMR vaccine and autism.6 They noted, however, that they could not exclude the possibility that MMR vaccine could contribute to autism in a small number of children.6

Varicella vaccine has been licensed for use in the United States since 1995, but it has been used for more than 20 years in Japan.7 The vaccine has been found to be 85 percent effective overall and 97 percent effective in preventing moderate to severe disease.7 As the number of varicella-immunized children increases, the incidence of wild-type varicella decreases. Unvaccinated children consequently have less chance of catching natural disease in childhood, but they are at greater risk for becoming infected in adolescence or adulthood, when complications and death from the disease are more likely. Although a small percentage of vaccinated children contract varicella each year, these illnesses are much less severe than those occurring in unvaccinated children or adults.

Almost one quarter of parents believe that too many immunizations could weaken their child's immune system.8 However, newer vaccines contain fewer antigens than older vaccines and have not been demonstrated to increase susceptibility to infection.9 In fact, failure to immunize exposes the child to developing not only the disease but also potential secondary complications, such as post-varicella group A beta-hemolytic streptococcal infection.9 In one study,10 unvaccinated children in Colorado were 22 times more likely to develop measles and almost six times more likely to develop pertussis than were vaccinated children. Even immunized children had a greater relative risk of developing disease because of the increased risk of disease posed by the unvaccinated children.10

Factual information may or may not change the minds of parents who express concerns or actively refuse to immunize their children. Physicians may wish to probe the underlying reasons for a parent's decision and allow the parent the opportunity to change the decision at a later date. However, family physicians should be knowledgeable about immunization indications, contraindications, and controversies.

Physicians must provide parents with a current Vaccine Information Statement (VIS) each time a vaccine covered under the National Vaccine Injury Compensation Program is administered. Copies of each VIS can be obtained from the Centers for Disease Control and Prevention ( or the Immunization Action Coalition ( Other immunization resources include the National Network for Immunization Information (; the Vaccine Education Center at the Children's Hospital of Philadelphia (; and the Society of Teachers of Family Medicine Group on Immunization Education ( The latter site has a Palm-based personal digital assistant (PDA) program called “Shots 2003” that can be downloaded at no charge.

Should parents continue to refuse immunization for their child, the physician may wish to have them sign a Refusal to Vaccinate form that is available from the American Academy of Pediatrics

Case scenarios are written to express typical situations that family physicians may encounter; authors remain anonymous. Send scenarios to Materials are edited to retain confidentiality.

This series is coordinated by Caroline Wellbery, MD, associate deputy editor.

A collection of Curbside Consultation published in AFP is available at

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