Risky Business: Challenges in Vaccine Risk Communication

Concern over vaccine safety has been a major determinant of immunization policy—from passage of the Biologics Control Act in 1902 to the recent American Academy of Pediatrics (AAP) and Advisory Committee on Immunization Practices (ACIP) recommendations for expanded use of inactivated polio (IPV) and acellular pertussis vaccines.1-4 With the availability of new vaccines and vaccination options comes the challenge of how best to communicate these options to patients and their parents. Lessons from the field of risk communication on predictors of risk acceptability and vaccination decision heuristics provide insight into why some parents resist vaccination. This article provides a historical perspective on vaccine adverse events and applies lessons from risk communication research to help physicians improve their ability to discuss vaccine risks.Immunizations have been described as the single most effective health intervention after clean water and sewage disposal,5 and have an extraordinary safety record. However, public policy has long reflected concern for the safety of vaccines and related biologics. In 1902, Congress passed the Biologics Control Act in response to the death of 13 children who had received injections of diphtheria antitoxin contaminated with tetanus toxin.6 This act required biologics to be manufactured in a manner that assured their safety, purity, and potency. Responsibility for these regulations was assigned originally to the Hygienic Laboratory of the Public Health Service, which evolved into the National Institutes of Health. The regulation of biologics including vaccines was transferred to the Food and Drug Administration (FDA) in 1972.The first published accounts of serious adverse events after whole cell pertussis vaccine occurred in 1933 with Madsen's7 report of two deaths within 48 hours of immunization, and in 1948 with the report in Pediatrics by Byers and Moll8 of encephalopathy after diphtheria and tetanus toxoids combined with whole-cell pertussis vaccine (DTwP). In 1955 the Cutter incident occurred, in which incompletely inactivated Salk vaccine was associated with over 200 cases of paralytic poliomyelitis.9 By the 1970s the incidence of many vaccine-preventable diseases had decreased significantly and concern over safety of whole cell pertussis vaccine surfaced in Japan and Europe.10 Pertussis immunization rates plummeted in several countries. Outbreaks of pertussis followed, leading to the development of an acellular pertussis vaccine (DTaP) in Japan.11The pertussis debate raging in Europe and Japan reached the United States in 1982, when the Emmy Award-winning television program,DPT: Vaccine Roulette, was aired with allegations of serious neurologic sequelae after DTwP.12 This was followed by the publication of Coulter and Fisher's book, DPT: A Shot in the Dark, in 1986.13 A dramatic increase in diphtheria, tetanus, and pertussis vaccine (DTP) litigation led to the withdrawal of several manufacturers from the marketplace. The Centers for Disease Control and Prevention (CDC) began stockpiling DTP vaccine as a shortage loomed. With the nation's health at stake, the National Childhood Vaccine Injury Act of 1986 (NCVIA) was passed,14after a collaborative effort involving the AAP, consumer advocacy groups, and others. This act included several provisions relevant to vaccine safety, creating the National Vaccine Injury Compensation Program (VICP) and the Vaccine Adverse Event Reporting System and mandating comprehensive reviews of vaccine-related adverse events by the Institute of Medicine (IOM) and the development of vaccine information materials.The expanded role of DTaP and IPV vaccines in childhood immunizations is in direct response to vaccine safety considerations. Concerns about local and systemic reactions prompted the recent revisions to the ACIP and AAP acellular pertussis vaccine recommendations, despite the lack of data establishing conclusively a causal link between DTwP and serious sequelae.15 After over a decade of research to develop less reactogenic pertussis vaccines for infants, the FDA licensed acellular pertussis vaccines for the fourth and fifth doses in 1992 and for the primary series in 1996.16 DTaP is now the preferred product, with DTwP an acceptable alternative during the transition period.24Since 1980, an average of 8 to 9 cases of paralytic polio per year have been associated with the live, trivalent oral polio vaccine (OPV) in the United States, either through direct receipt or contact with a recipient.3 In 1994, the Western Hemisphere was certified by the World Health Organization to be free of indigenous wild polio.17 The greatly diminished risk of acquired paralytic polio from wild poliovirus, either indigenous or imported, prompted a reevaluation of the risks of OPV-associated paralytic polio. After much debate, the AAP and ACIP have moved toward expanded use of IPV.13 With the availability of new options comes the challenge of how to communicate these options to our patients. Moreover, pediatricians are occasionally faced with parents who question the need for vaccinations altogether.Why is vaccine risk communication so challenging? Perhaps the most important factor may be the lack of disease awareness. The dramatic decline of vaccine-preventable diseases has inevitably decreased public awareness of these illnesses, likely prompting greater reluctance to accept adverse reactions after vaccination. Another factor is the power of temporal association—ie, post hoc, ergo propter hoc—or what follows immunization must be caused by it. Neurologic sequelae after DTwP are one example of this logic. Although paralytic polio is a demonstrated risk after vaccination with OPV, many serious adverse events temporally associated with immunization lack a clear cause-and-effect relationship. In addition, vaccine risk communication is hampered by a lack of data. In 199118 and 199419 the IOM undertook extensive reviews of adverse events associated with childhood vaccines, and concluded that there was either no evidence or insufficient evidence to establish a causal relationship for two thirds of the conditions it studied. Moreover, experts often disagree about the interpretation of existing data, further confusing a public looking to science for answers. The rarity of an adverse event, the lack of defined clinical syndromes, and the absence of pathophysiological understanding limit investigation into adverse events. For example, no specific clinical syndrome or neuropathology has been defined for DTwP encephalopathy, despite more than five decades of DTwP use.Underlying this issue is the inherent tension between protecting public health and allowing individual autonomy. Some consumer advocacy groups formed from the DTwP controversy of the 1980s maintain the importance of parental choice in vaccinations.13 However, the enactment of state laws mandating immunizations for school entry, in large part responsible for wide vaccine coverage and the dramatic drop in vaccine-preventable diseases, is in direct collision with free parental choice. Some health care practitioners also support the concept of choice in vaccinations. For example, a survey of American chiropractors found that 81% of respondents believe immunizations should be voluntary.20 Currently, most states permit religious exemptions to vaccination requirements and 15 states permit philosophical exemptions (Joel Kuritsky, CDC, National Immunization Program, unpublished data). Reconciling patient empowerment with the goals of public health remains problematic.The media and other sources of public information play a role in vaccine risk perception.21 In 1994, media reports incorrectly attributed deafness in Heather Whitestone, the former Miss America, to the DTwP vaccine, although her condition was later confirmed by her pediatrician to be the result of Haemophilus influenzae type b meningitis.22 The irony that her condition was caused by an illness now preventable by vaccination may have been lost on the American public because of the media fanfare surrounding the initial report. This episode underscores the fact that health professionals are not the only source of vaccine information, which can come from family members, neighbors, and an array of media outlets such as newspapers, magazines, and television. More recently the Internet, with its home pages and electronic bulletin boards, has emerged with vast potential for information dissemination but without any editorial control, much less peer review.23 Even when presented with accurate information, parents and physicians may differ in how they interpret data and make decisions on risk. What then are the determinants of risk perception, and what risk communication approaches are available to the pediatrician?By and large, pediatricians are viewed as a credible source of vaccine recommendations, a notion supported by a recent study of private pediatric practices that indicated provider behavior may be the most important determinant of immunization rates.24The majority of parents follow their pediatrician's recommendation regarding immunizations, and may not engage in an independent decision-making process. However, a minority of parents question vaccination recommendations. For them, short explanations of risks and benefits may not suffice.Over the past two decades the field of risk communication has developed from the need to find more effective ways to communicate health risks. Researchers in this field recognized the discrepancy between how scientists explained health risks and what the public believed. Risk communication research has drawn from diverse disciplines such as cognitive and social psychology, behavioral decision theory, and risk assessment and management, and has concentrated on environmental hazards including nuclear reactors,25 chemical plants,26 and radon.27 A broad review of risk communication was conducted by the National Research Council in 1989.28 Theories developed in this field have only recently been applied to vaccine risk communication.29Of paramount importance is that individuals perceive risk differently. Although physicians may focus on the statistics regarding general vaccine effectiveness and known risks of vaccine-preventable diseases, parents making vaccination decisions may perceive risks in a broader religious, cultural, and personal context. Individual characteristics affect decisions to vaccinate; data from the CDC tell us that immunization rates vary by race, education, socioeconomic status, and other factors.30 For example, mistrust of the medical system by some African-Americans has been identified as a barrier to optimal health care and participation in clinical trials,31and was highlighted by the Clinton Administration's recent decision to issue a formal apology for the Tuskegee Syphilis Study.32Confronting reasons for undervaccination such as lack of access and missed opportunities may be easier than addressing issues of trust and cultural perspective.Other attributes of risk also affect risk acceptability and may complicate parental risk decisions.33 Voluntary, controllable risks are more acceptable than involuntary risks.29 Consumer groups advocating greater parental choice in vaccination contend that state laws mandating vaccination for school entry render vaccination an involuntary risk, and thus less acceptable.29 Researchers have uncovered another way in which the perception of control influences parental vaccination decisions. Meszaros et al34 demonstrated that parents refusing vaccination were more likely than parents who vaccinated their children to agree with the statement, “If there were no vaccination given to my child, I could prevent the disease.” Thus, some parents may not accept vaccination recommendations because they perceive control over events in ways not recognized by the pediatrician.Additional factors may influence the acceptability of risks. Some risk communication researchers suggest that natural risks are generally more acceptable than man-made risks.35 At an IOM forum on polio vaccine policy, an advocate for alternative therapy argued that immunity acquired after natural infection is often preferable to vaccine-induced.36 This logic neglects the often severe morbidity and mortality associated with vaccine-preventable diseases, as well as the fact that some vaccine-preventable diseases induce no significant immunity (eg, tetanus). In addition, the acceptability of a risk is determined by whether it induces fear or dread and whether it is memorable. Any event adversely affecting the well-being of a child is dreaded, and risks that are memorable are more aversive than those that are not. For example, parents' recall of the fever and fussiness after DTwP in their infant may influence their acceptance of further vaccinations.Finally, risk communication researchers have demonstrated that some parents are unlikely to undertake a risk control measure unless they perceive both a serious threat and some control over the risk.37 When a perceived threat is low, individuals are unlikely to accept a health intervention regardless of the efficacy of that intervention. Thus, a decision to vaccinate is most likely to be made by a parent who recognizes the threat of vaccine-preventable illness and perceives vaccination as an appropriate resource to control that risk.How risks are perceived depends, in part, on how the message isframed. Studies have shown that an option described in terms of benefits may result in a different decision than the equivalent option described in terms of risks.3839 Applying this to vaccines, risk communication that emphasizes lives saved by vaccination may be more effective in promoting vaccination than communication that mentions the lives lost despite vaccination. In addition, the extent to which an individual perceives a health intervention as risky may determine how a message is processed and what action is taken.38 Research in this area suggests that for parents who view vaccines as generally safe, emphasizing the benefits of vaccines may be the most successful approach to encourage vaccination. For those parents who question vaccine safety, a more effective approach may be to frame the decision in terms of the risks of illnesses preventable by vaccination.Because most risk decisions involve more information than can be processed readily, individuals tend to simplify. An intervention such as immunization is often categorized as safe or unsafe without acknowledging the spectrum in between. Heuristics are cognitive shortcuts that people use to simplify complex decisions and judgments. Parents may use heuristics to quantify risk. In some cases, heuristics may result in a decision not to vaccinate.The heuristics individuals use to make risky decisions includecompression, or overestimating the frequency of rare risks and underestimating the frequency of common risks.40Concerns about DTP encephalopathy and vaccine-associated paralytic polio, which are rare, may be increased by use of this heuristic. Moreover, the availability of an event (one that is accessible or easily remembered) can lead to overestimation of its frequency; witness the effectiveness of sensationalized media reports alleging vaccine injury.Several studies have elucidated an omission bias, which explains the reluctance for certain parents to vaccinate their children.344142 That is, they withhold vaccinations because of the perception that actions (commissions) are more harmful than inactions (omissions). A study by Ritov and Baron41using a hypothetical vaccine scenario found that some individuals would feel more responsible if their child died after a vaccination than after a vaccine-preventable disease. This study also demonstrated the preference of some individuals to eliminate risk, with 23% of individuals in one experiment indicating that they would vaccinate their child only if the risk of vaccination was zero. Moreover, when given a choice, individuals tend to avoid ambiguity.43 For example, a risk from a known disease may be more acceptable than an equivalent or smaller risk that is perceived as more ambiguous (eg, from a new vaccine). This heuristic may be operative in some parents' avoidance of the varicella vaccine. 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