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Parents can express their doubts about vaccination in various ways: they can have their child vaccinated, although they are not sure it is the best thing to do; they can delay immunization; or they can simply refuse to have their child vaccinated. The most frequent reason for nonvaccination is concern that the vaccine might be harmful.
ABSTRACT:Parents can express their doubts about vaccination in various ways: they can have their child vaccinated, although they are not sure it is the best thing to do; they can delay immunization; or they can simply refuse to have their child vaccinated. The most frequent reason for nonvaccination is concern that the vaccine might be harmful. Children with nonmedical exemptions are at increased risk for acquiring and transmitting vaccine-preventable diseases. Recent outbreaks of measles and rubella show that herd immunity cannot completely protect vaccine refusers from contracting these diseases. Historically low disease rates, as in the case of invasive Haemophilus influenzae type B disease and mumps, may not be proof that the risk of epidemic diseases is remote.
Vaccines are among the most successful and most cost-effective tools for preventing infectious diseases and their complications. High immunization coverage in the United States has led to significant reductions in the morbidity and mortality of vaccine-preventable diseases.1 The coverage estimates for the individual vaccines have been reported to be more than 90%.2 Much of the success can be attributed to the public trust and support of the National Immunization Program.
Despite the overwhelming success of immunization and school mandates in the United States, sustaining support for immunization remains a challenge. Several factors contribute to parental refusal of vaccines. One is the public perception that the severity and susceptibility to vaccine-preventable diseases have decreased because of the reduction in these diseases.3 Another is heightened parental concerns regarding vaccine safety as a result of expanding childhood immunization requirements and increased media coverage of alleged associations between vaccinations and chronic illnesses.4 Here I will review these and other factors that lead to vaccination delay and refusal and highlight the findings and lessons learned from a few recent outbreaks of vaccine- preventable diseases. I will also offer suggestions on how to strengthen public trust in vaccination.
Public Perception of Vaccines
Vaccines are the victims of their own success. In the absence of vaccine-preventable diseases, many parents fear vaccines more than the diseases known to them only vaguely. In addition, the majority of practicing physicians in the United States, although advocating for vaccination, have no personal experience with most vaccine-preventable diseases. As many of these diseases become distant memories, consumerism increases along with the individual's desire to understand health issues and assume responsibility for his or her own health decisions.5 With an increased number of vaccines now mandated by state laws, and the inherent coerciveness of mandates, the public has become hesitant and distrustful of vaccination.
The general climate of distrust has been amplified indirectly by exposure of dishonesty in the corporate world, politics, academia, and government. Mass media increasingly shapes public perception, and controversy and bad news are known to attract more readers and viewers than good news.5 Allegations of vaccine harm garner disproportionate attention. Information technology, such as the Internet, has increased access to information-and misinformation-about immunization.5 The Internet also facilitates social networking, which empowers and reinforces the zeal of even relatively small numbers of people with similar views of skepticism in immunization. Therefore, acceptance of immunization has eroded.5,6
In the United States, one result of the public's distrust in vaccines is a rise in vaccine exemption rates from school entry immunization requirements for philosophical or personal reasons.7 In 2009, for example, the private schools in Florida, California, Oregon, Vermont, and Minnesota reported rates of vaccine exemption for philosophical or religious reasons of 2.2%, 3.9%, 9.7%, 12.9%, and 15.9%, respectively; the rates were lower for the public schools.8 According to Omer and colleagues,7 states that permit personal belief exemptions have higher nonmedical exemption rates than states that offer only religious exemptions. States that easily grant exemptions also have higher nonmedical exemption rates. The Omer study showed that these state policies (easy granting of exemptions and allowing exemption on the basis of personal beliefs) are associated with increased pertussis incidence.7
Vaccine Safety Concerns
Vaccine safety concerns are important factors that can diminish parents' willingness to vaccinate their children.9 Widely publicized and often dramatically presented allegations of adverse events after immunization have raised anxiety levels among parents. One of the main public health concerns on vaccine safety was triggered by the 1998 report published in The Lancet. that linked measles-mumps-rubella (MMR) vaccination with behavioral disorders. The publication was subsequently retracted after the judgment of the United Kingdom General Medical Council that the research results were unreliable, that there were conflicts of interest, and that the approval by the local ethics committee was proved to be false.10 In fact, several studies indicate that there is no link between MMR vaccination and any behavioral disorders, including autism.11-14
In a survey of 3924 parents conducted by the CDC from 2003 to 2004, 9% of parents accepted vaccination, although they were not sure it was the best thing to do; 13% delayed their child's vaccination; and 6% refused vaccination for their child.15 Therefore, parents can express their doubts about vaccination in a variety of ways:
• They can have their child vaccinated, although they are not sure it is the best thing to do.
• They can delay immunization.
• They can simply decide not to have their child get the vaccine.
Concern about vaccine safety is associated with all parent groups above, although most parents who delay vaccinations do so because they are concerned about potential negative effects of their child being ill and receiving a vaccine at the office visit. Parents who are unsure whether vaccination is the best thing to do are typically white and older and live in the western region of the United States. In another study by Gust and colleagues,16 a larger proportion of mothers older than 40 years fell into a group most worried about immunizations for their children, perhaps because these women have a tendency to be more protective and/or more confident in resisting the recommendation.
Parents who refuse or exempt vaccination for their children perceive that their children have low susceptibility to vaccine-preventable diseases, that the severity of the diseases is low, and that the efficacy and safety of the vaccines are low.3 They are also more likely to obtain vaccine information from the Internet and groups opposed to immunization and to have providers who offer complementary or alternative medicine. The most frequent reason for nonvaccination is concern that the vaccine might be harmful. They also believe that children receive too many vaccines.17
Parents in general have more concerns about the safety of newer vaccines, such as the human papillomavirus (HPV) vaccine, varicella vaccine, and meningococcal conjugate vaccine.9 This is probably because these vaccines have shorter track records on safety and, in the case of the HPV vaccine, complex issues surround its provision, especially sexual risks (see page S15 for a pro/con discussion on the HPV vaccine for boys). Parents who refuse vaccines for their children tend to be white, higher-salaried, and college-educated.15,18 One possible reason for vaccine refusal among this population may be that a larger proportion of white parents homeschool their children and some states do not enforce immunization for homeschooled children.
Parents who delay immunization for their children tend to be non- Hispanic black and unmarried and have no college education and multiple children at home.15,19 They typically have 2 or more vaccination providers and use public vaccination providers. One reason for the delay in immunization may be the unmarried mother's inability to keep her children's medical appointments because of a lack of financial resources and/or child-care support from a spouse. In one study, about 1 in 4 US children had delayed vaccination for more than 6 months and for 4 or more vaccines during the first 24 months of life.19 Therefore, minimizing delayed or missed vaccination and vaccine refusal is equally important to the health of individual patients and overall public health.
Many opponents of immunizations may base their opposition on religious beliefs. Although their underlying reasons vary, their convictions are similar. Certain Christian groups believe that immunization violates their religious freedom and individual choices.20 Some Amish communities view health as a gift of God and not solely the result of preventive medicine.21 The Amish consciously avoid dependence on government and might consider acceptance of free vaccination a form of government welfare. Muslim fundamentalists claim that it is a Western plot to sterilize Muslims and see immunization as an attempt to subvert the will of God.22,23 Catholics oppose vaccines that are manufactured using human cell lines derived from aborted fetuses.24 Discussions about the effectiveness of vaccines and the risks of disease are unlikely to influence or change the beliefs in these groups.
RISK OF VACCINE-PREVENTABLE DISEASES
Children with nonmedical exemptions are at increased risk for acquiring and transmitting vaccine-preventable diseases. A report from Colorado indicated that children of parents who refused pertussis immunizations had a 23-fold increased risk of pertussis compared with children of parents who accepted immunizations; herd immunity did not completely protect vaccine refusers from pertussis.25 Children of parents who refused varicella immunizations were at 9-fold increased risk for varicella compared with children of parents who accepted immunizations.26
Diseases acquired or imported from abroad. Although many vaccine-preventable diseases are rare today in the United States and other developed countries, the outbreaks in such settings have occurred when the pathogens are acquired or imported from abroad.
In 2004, a large rubella outbreak occurred in an unvaccinated, sociogeographic-clustered orthodox protestant community in the Netherlands.27 The outbreak subsequently spread across the Atlantic to a similar community in Canada. The infection also occurred in pregnant women and resulted in a high burden of congenital rubella syndrome.
In 2007, a Japanese boy who traveled to the United States to participate in an international youth sporting event in Pennsylvania became ill with measles.28 A further epidemiological investigation identified 6 additional measles cases in 3 states that were linked to the index case. The identical genotype sequences of the virus obtained from the index case and from the contact cases confirmed the link between the cases. The 6 contact cases were:
• An airline passenger who was seated in the row in front of the index patient on a Detroit-Baltimore flight.
• A Michigan airport officer who was exposed to the index patient in the airport customs area and who possibly infected his coworker.
• A corporate sales representative who had contact with the index patient in Pennsylvania
• Two college students who met the corporate sales representative during a sales event in Texas.
• Another Japanese boy who had contact with the index patient in Japan and then traveled to the United States to attend the same sporting event.
In 2008, an intentionally unvaccinated boy who was unknowingly infected with measles returned to San Diego from Switzerland.29 This resulted in more than 800 exposed persons and 11 secondary cases of measles, 9 of which were in children of parents who refused immunization because of personal beliefs.
Lessons learned from these outbreaks are highlighted in the Box.
Resurgence of epidemic diseases within the United States.
Historically low disease rates may not be proof that the risk of epidemic diseases is remote. This is evident by the large nationwide outbreak of mumps in the United States in 2006.30 The outbreak was preceded by a period of very low disease incidence, and it occurred mostly among college attendants of whom waning immunity was secondary to a lack of natural exposure to mumps.31 These young adults entered college at a time of increased risk of the importation of mumps virus from abroad (eg, when the 2004 to 2005 mumps epidemic in the United Kingdom was peaking).32
A more recent outbreak of invasive Haemophilus influenzae type b (Hib) disease in 2008 involved 5 children in Minnesota.33 The implementation of Hib vaccination in the early 1990s has led to a 99% decrease in Hib disease in children in the United States.34 These 5 cases were the highest number reported in Minnesota since 1992. Three of the children received no vaccinations because of parent refusal. One child was too young to complete the primary series of the vaccine. Another child had hypogammaglobulinemia. The cases occurred during an Hib vaccine recall and continuing national Hib vaccine shortage that began in late 2007. The increase in the number of Hib cases in Minnesota probably reflects an increase in carriage and transmission affecting those with suboptimal vaccination or a weakening of herd immunity during the shortage.
HOW TO STRENGTHEN PUBLIC TRUST
Additional steps can be taken to strengthen public trust in immunization. Clinicians and other health care providers play a crucial role in parental decision making with regard to immunization.
Provide assurance and information for parents. Health care providers are cited by parents, including parents of unvaccinated children, as the most frequent source of information about vaccination.3,35 Parents who are unsure about vaccinating their child are willing to discuss their concerns with a trusted provider and want the provider to offer information relevant to their specific concerns.36 The main reason parents change their minds about delaying or refusing a vaccination for their child is the assurance and information received from their health care providers.15 Therefore, the provider's knowledge and attitudes are crucial factors for the success of immunization.
Address your own concerns about vaccine safety. In a study on vaccine knowledge and practices of primary care providers, the majority of providers for exempt children had favorable attitudes about vaccine effectiveness and benefits, similar to those of providers of nonexempt children.37 However, providers of exempt children were less likely to have high confidence in vaccine safety. They were more concerned that a child's immune system could be weakened by too many immunizations, and they believed that it is better for children to develop immunity by getting sick than by being immunized. The origin of these concerns needs to be evaluated and addressed in effective ways. Education for providers regarding immunization and vaccine safety during professional schooling, clinical training, and continuing professional education may need to be improved. Ongoing assessments of both the public's and provider's vaccine safety concerns coupled with risk communication from credible sources need to be enhanced.
Show some respect. Given the diverse reasons for parental refusal or delay in immunization, providers should address such issues by respectfully listening to parental concerns, honestly sharing what is known and not known about the risks and benefits of the vaccines,
explaining the risk of nonimmunization, and discussing the specific vaccines that are of concern.38 Continued refusal after adequate discussion should be respected unless the child is put at significant risk for serious harm. Parents may change their minds in the future. Therefore, it is important to maintain such discussions in the subsequent visits. Denial to provide care for a family that refuses vaccination should be discouraged (see page S16 for a pro/con discussion of this point).
FROM THE PLANE TO YOUR OFFICE Lessons Learned From Recent Outbreaks of Vaccine-Preventable Diseases
• Persons in routine contact with international travelers can be exposed to any vaccine-preventable disease, and it could lead to an outbreak over a large geographic area.
• The clustering of vaccine refusal can provide a reservoir of susceptibility, enhancing spread of disease to the larger community.
• Herd immunity cannot completely protect vaccine refusers from contracting the disease.
• Although the risk of acquiring the disease from abroad is high when the country of origin is less developed with an inadequate health care infrastructure, the risk remains even when the country of origin is developed with an adequate health care system (eg, the Netherlands, Japan, and Switzerland).
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