Every Child By Two Campaign: The Failure of Individual-Level Behavior Change – Lauren Kleimola

Rosalynn Carter and Betty Bumpers founded Every Child By Two (ECBT) in 1991 in reaction to the measles outbreaks in the United States between 1989-1991 (1-2). The goal of ECBT is to raise awareness of the need for timely immunizations and provide support for every child in the United States to be immunized by age two. The primary method for achieving nationwide immunization is through education of different sectors of the population. Parents, elected officials, and healthcare providers constitute the three focus areas for the campaign. ECBT also helps to secure funding for programs providing vaccinations to uninsured and underinsured children. Further, ECBT assists the implementation of electronic vaccination registries throughout the country. The objective of the campaign’s approaches is to persuade all parents’ of the critical importance of vaccinations and offer the means to achieve timely and complete immunization. Unfortunately, ECBT is unsuccessful as a behavior change campaign because it does not address the true motivators of and barriers to human behavior. The campaign will not result in nationwide immunization of children without a deeper understanding of the factors that shape parents’ decisions to vaccinate or not vaccinate their children.

Assumes that behavior is rational

The ECBT campaign relies on the Health Belief Model (HBM) to persuade caretakers to vaccinate their children. The HBM theorizes that when individuals make health-related decisions they weigh the threat of the disease and the benefits of an action against the barriers to taking action (3). If the perceived threat of disease and benefits of action are greater than the perceived barriers to the action then the individual will engage in the health behavior, according to the theory (4). Perceived susceptibility and perceived severity are two components of the HBM theorized to determine the degree to which individuals assess the threat of a given disease (5). ECBT attempts to increase the number of parents choosing to vaccinate their children by both amplifying the perceived threat of vaccine-preventable diseases and by decreasing the barriers to vaccination. The campaign increases perceived threat of disease in two ways, increasing perceived susceptibility to and perceived severity of disease. Using the HBM to create behavior change assumes that people logically evaluate risks and benefits before taking an action. Unfortunately, people do not use reasoned thought in order to make rational decisions (6). Therefore, the ECBT campaign relies on the flawed assumption that human behavior is rational when it utilizes the HBM to improve childhood immunization rates.

The campaign increases perceived threat of disease in two ways, increasing perceived susceptibility to and perceived severity of disease. On the ECBT website, a public service announcement titled “Timely Immunizations” uses images to increase caretakers’ perception of children’s susceptibility to disease and audio to increase caretakers’ perception of the severity of the diseases (7). Images of young children covered with the names of diseases, such as mumps and whooping cough, play during the video (7). Visuals that associate children with disease relay the message that children are at risk for, or are susceptible to, these diseases. At the same time, Rosalynn Carter tells listeners that “children still die and suffer from vaccine-preventable diseases,” increasing the perceived severity of disease (7). Attempting to change caretakers’ behavior by amplifying the threat of disease assumes that caretakers are currently unaware of these threats and that once they are better informed, they will make the decision to vaccinate their children.

The campaign also models the HBM by decreasing the barriers to immunization. ECBT minimizes barriers in two ways: helping to secure funding for vaccines and promoting efficient organization of vaccine registries. ECBT funds programs that help make vaccines readily available to uninsured or underinsured children. In doing so, ECBT reduces or eliminates financial burden as a barrier to childhood vaccination. The campaign also provides support to implement electronic vaccination registries in healthcare facilities. Electronic registries of vaccines help healthcare workers to keep track of children’s immunization histories. Improving organization within healthcare facilities promotes timely and complete immunization, reducing inadequate healthcare services as a barrier to vaccination. ECBT employs multiple strategies taken from the HBM to improve childhood vaccination rates, concurrently decreasing barriers to vaccination and amplifying the threat of disease. By creating a campaign based on the HBM, ECBT relies on the assumption that parents will weigh the benefits of vaccination against the barriers to vaccination and make a decision based on the outcome.

The assumption that providing information and increasing access to vaccines will lead to improved immunization coverage is flawed because individuals do not engage in objective and logical thought processing to come to rational decisions (5). A rational decision is one that an individual would make repeatedly, regardless of how a question or situation is presented, or framed (8). However, situational factors interfere with rational thought and consequently alter people’s behavior (9-11). Far from objective, emotion, impulse, and instinct shape human decisions (9-11). Amplifying perceived threat of disease and reducing barriers to immunization are behavior change methods, taken from the HBM, that assume reasoned thought will guide behavior. The ECBT campaign, grounded in the flawed assumption that human behavior is rational, fails to effectively intervene in caretakers’ decision-making processes. Without impacting caretakers’ behaviors regarding immunizations, the campaign will not achieve its goal of increasing childhood vaccination rates.

Frames vaccination using health as a core value

Framing theory suggests that an issue can be viewed from multiple perspectives (12). The perspective with which one views an issue determines the values one associates with the issue and the opinions one forms (13). Therefore, the way in which an issue is framed has a profound impact on the values an individual assigns to the issue and these values will determine individuals’ opinions and behaviors (14). It seems intuitive then that an effective campaign first determines the core values of its target audience, along with its needs and wants, and then frames the campaign according to those values, needs, and wants (15). The Truth campaign, for example, successfully reduced cigarette smoking among teenagers by appealing to teens’ desires for independence and rebellion (16). The success of this program was in stark contrast to the failure of Just Say No campaigns that preached to adolescents about the dangers of drugs (17). In fact, two of five Just Say No campaigns were significantly less effective at reducing adolescents’ willingness to try drugs and improving their confidence in handling situations involving drugs when tested against a control campaign about video and news production (17). The evaluation of past campaigns shows that understanding the values of an audience before developing and using a campaign is essential, as using the wrong values can result in the opposite effect of the desired outcome.

The ECBT campaign uses health as its core value to encourage parents to vaccinate their children. A written message to parents on the ECBT website states, “it is so important to immunize your child on time, every time. Vaccines have saved millions of lives over the years and prevented hundred of millions of cases of diseases” (18). Also available for parents are sections on vaccine safety and descriptions and images of vaccine-preventable diseases. These messages emphasize the importance of immunization to health, a value that past campaigns show is ineffective at prompting behavior change (15).

Past public health campaigns have overwhelmingly tried to change behavior by using health as a core value (19-24). Despite decades of these campaigns, indicators of public health in the United States, such as exercise rates, consumption of fruits and vegetables, and prevalence of obesity, continue to worsen (25). Research on the association between risk awareness and engaging in risky behavior has helped to illuminate that health does not drive human behavior (26-28). Studies show that individuals engaging in unhealthy behaviors are frequently aware of the health risks associated with those behaviors, so lack of knowledge is not the main cause unhealthy behavior (26-28). Knowledge of health risks among individuals engaging in unhealthy behaviors implies that protection of one’s health is not a strong enough force, or value, to change behavior. Understanding that health is not a core value among many populations explains why campaigns using health as a core value have often failed. ECBT, like past failed campaigns, frames its message using health as a core value. Without shifting the frame of childhood vaccines to appeal to the values, wants, and needs of its audience, ECBT will neither change caretaker behavior nor increase childhood vaccinations.

Ignores the context in which behavior occurs

A final critique of ECBT’s campaign strategy is that it ignores the context in which individuals make their decisions. Previously discussed with the irrationality of human behavior, the context in which a decision is made influences the outcome of that decision (29-30). According to social-ecological theory, evaluating the context in which a decision or behavior occurs recognizes that outcomes result from an interaction between situational and personal factors (31). Therefore, public health professionals cannot attribute behavior entirely to the individual, but must consider factors such as the social, political, and economic circumstances acting on the individual. Yet, many public health campaigns aim to change behavior through altering individual traits (e.g. attitudes and beliefs) without accounting for situational factors (e.g. social norms and access to healthcare) that constrain or assist individuals’ ability to change their behavior (32-33).

When a campaign targets only individual traits, as ECBT does, it overestimates the control the individual has in determining his or her own behavior (34). ECBT includes information relating to vaccine safety on its website (35). The campaign is attempting to change individual traits, specifically attitudes toward vaccination, by providing educational materials, without considering the context in which people make decisions. The campaign relies on each individual to make an informed decision regarding vaccine safety in isolation from external influences. As seen through social-ecological theory, targeting only individual traits and not the broader context in which the individual interacts with his or her surroundings does not provide the necessary means for behavior change (31). In fact, addressing fears surrounding vaccines may hinder the campaign’s goal of increasing childhood vaccination rates by reminding parents of reasons why they should not have their child vaccinated, having the opposite effect of what the campaign is hoping to achieve (36).

Trend in social norms is a defining component of the context within which individuals encounter the issue of childhood vaccination (37). Social norms, a set of rules, customs, and values within a society that determine social behavior, are upheld by the “embarrassment, anxiety, guilt and shame that a person suffers at the prospect of violating them” (38-39). After the release of the article by Wakefield et al. incorrectly linking Autism and the MMR vaccine (40), childhood vaccination rates plummeted, falling from 92% coverage in 1995-96 to 80% in 2003-04 in the United Kingdom (41). The downward trend in vaccination spread across the globe, initiating a shift in social norms toward skepticism of vaccines (37). It is crucial for campaigns aiming to increase immunization coverage to understand societal trends. Broadening the study of behavior from the individual to society offers explanations for irrational behavior and provides an alternative means for behavioral interventions.

ECBT’s narrow focus on individual-level behavior change restricts its effectiveness. Understanding that vaccines do not cause Autism is insufficient to change the behavior of individuals feeling shame at the prospect of violating social norms (42). The campaign will not lead to a rise in childhood immunization coverage unless it acknowledges the context in which individuals make vaccine-related decisions by addressing changes in social norms.

An Alternative: The Live Free Club

I propose an alternative to the Every Child By Two Campaign that targets parents of young children as a group and frames vaccination using freedom as a core value. As opposed to using a campaign strategy, I propose a social club for first-time parents and parents of young children. A social club provides a new context in which parents decide whether or not to vaccinate their children, acknowledging that context plays a vital role in determining parents’ behavior. The club name, Live Free, highlights its focus on parents’ ability to retain freedom, a prominent core value, after a child is born (15). The target audience is parents of young children, with a particular focus on first-time parents, living in the United States. The average age at first birth in the United States is 25 and has been climbing over the past four decades, so the club is centered around the values, needs, and wants of parents ranging from their mid-twenties to early-thirties (43).

Live Free believes in the freedom of parents to lead a fulfilling, well balanced, and happy life. The purpose of the club is to allow parents of young children to regain freedom they may feel they have lost after the birth or adoption of a child, or to avoid that sense of loss altogether (45-46). Freedom and autonomy are therefore the driving values of the club and help define the common beliefs of club members. Live Free accomplishes its purpose by connecting parents who live in the same region and providing different services, activities, and benefits. Services include a list of prescreened babysitters and discussion boards for parents to connect with one another. Activities give parents a chance to meet in person and involve trips to sporting events, museums, and hiking trips. Some trips are for parents and children while others are just for parents, showing that life with children can involve social engagements but also recognizing parents’ desires for the social lives they had before having children (45). Membership also includes discounts to local restaurants, gyms, museums, movie theaters, etc., offering relief from the financial restrictions to freedom that come with having a child.

The club starts in select regions of the United States, using the National Immunization Survey to define target areas with the highest vaccination coverage, and then expands to other regions until reaching nationwide coverage (44). Mass media, including television commercials and magazine ads, will promote Live Free. Advertisements have images of young, happy parents engaged in fun activities that highlight their freedom to enjoy life and fulfill their sense of adventure. The mass media strategy recruits parents through social norms, again addressing the context in which behavior occurs. Membership is for individuals who have had a child within the last five years, creating a cohort and sense of belonging among parents, and commit to having their children fully immunized. While commitment to immunization is a part of membership, it is not the focus of the club.

Recognizes that behavior is irrational

Live Free does not depend on human behavior to be rational in order to improve childhood vaccination rates. Live Free invokes social norms and Cognitive Dissonance Theory to change behavior instead of using logic and reason as the ECBT campaign does. The club improves immunization coverage by first changing parents’ behavior, allowing attitude change to follow behavior change. Changing behavior before attitudes does not require parents to be rational. Instead, it models Cognitive Dissonance Theory by relying on parents to react to discomfort incurred by inconsistencies between behavior and attitudes by adjusting their attitudes (47).

Previously discussed in the section on context, social norms influence individuals’ behavior (48). People are driven by a need for acceptance and consequently behave in ways of which they believe others will approve (48). Further, people model their own behavior after observed social norms (48). Frequent and intense media messages can make behavior or values associated with the advertisements appear normative (49). Thus, a high-intensity media campaign using young parents as spokespeople for Live Free will make membership appear to be a social norm. The establishment of membership as a norm will appeal to individual’s desire to belong and follow socially acceptable behavior by also joining. Concurrently, joining Live Free requires that members commit to fully vaccinating their children, making immunization appear to be a norm as well. As human behavior is guided by social norms, parents will join Live Free and vaccinate their children, leading to an increase in childhood vaccination coverage.

After Live Free changes parents’ behavior, cognitive dissonance will change their opinions and beliefs regarding vaccination. Cognitive Dissonance Theory proposes that it is unpleasant for people when two cognitions (ideas, beliefs, opinions) they hold are inconsistent with one another, or in other words, are dissonant (50). If behaviors (which becomes a cognition, e.g. “I am a smoker”) and beliefs are incompatible, an individual will more frequently change their beliefs over behaviors in order to reduce dissonance (51). Similarly, a person will amplify the positive attributes of a chosen decision and amplify the negative attributes of a forgone option in order to reduce dissonance after making a decision (52). Unlike the HBM, “dissonance theory does not rest upon the assumption that man is a rational animal; rather, it suggests that man is a rationalizing animal – that he attempts to appear rational, both to others and to himself” (52). Live Free uses cognitive dissonance by first getting parents to join and committing to vaccinate one’s children, knowing that parents will reduce any dissonance between membership and their previously held beliefs regarding vaccination through attitude change. Live Free takes advantage of parents’ irrationality by invoking social norms to recruit parents and thereby vaccinate their children, then allowing cognitive dissonance to change attitudes toward vaccination of previously skeptical parents.

Reframes vaccination using freedom and control as core values

The failure of health as a value to motivate behavior change indicates that to successfully change health-related behavior, the issue must be reframed using a higher core value (15). Following successful marketing strategies, new parents’ needs, wants, and values are first identified and then childhood vaccinations are reframed according to the findings (53). Previous research indicates that freedom and control are strong core values of new parents (45-46). New mothers report losses of freedom and independence; time for themselves, their partner, and their friends; and control over one’s life (45). Women also indicate strong desires to regain the freedom and control they feel they have lost (45). Similarly, men associate parenthood with a loss of freedom (46).

Live Free reframes vaccination using freedom and control as core values. In order to effectively market childhood vaccination with these new core values, Live Free makes a promise to parents that fulfills their needs and provides support for that promise (15). The promise of Live Free is that if you become a member, you will live a fulfilling, happy, and balanced life and regain the freedom and control that was lost with the birth of a new child. Immunization of one’s children becomes a part of this promise as commitment to vaccinating one’s children is embedded in membership. Just as being a member of Live Free promises freedom and control, so does immunizing one’s children. The support for this promise comes from advertisements. Ads display new parents engaged in activities that parents feel they lost the freedom to partake in when their child was born, such as social engagements with friends or exercising to take care of oneself. Visual images of peers in control of their lives will appeal to parents’ emotions, encouraging them to join Live Free in order to achieve the same level of freedom and control. Reframing childhood vaccination using freedom and control as core values is a more effective way to increase vaccination coverage than the use of health as a core value because freedom and control appeal to the wants of new parents. Live Free increases immunization rates by making vaccination of one’s children a characteristic of members and also fulfilling parents’ desire for greater freedom and control through membership.

Changes the context in which behavior occurs

A final way in which Live Free succeeds in changing parental behavior toward vaccination where ECBT does not is by changing the context in which parents make their decisions. The release of the Wakefield paper initiated a downward trend in vaccination rates and established a social norm of skepticism toward vaccines (37). Understanding that social norms are driving immunization rates, Live Free changes attitudes and behavior at the societal-level instead of at the individual-level. The majority of new parents are recruited into Live Free through diffusion of innovations and their behaviors and attitudes toward vaccination are changed through this new social network.

Diffusion of Innovations Theory separates society members into early adopters, early majority, late majority, and laggards (54). Early adopters are individuals who are willing to take risks and adopt a new idea before the majority (54). Live Free targets the early adopters by initiating the club in areas of the United States with the highest vaccine coverage. Areas with high vaccine coverage will have the fewest number of parents who refuse to vaccinate their children and therefore the fewest number of parents who have negative opinions of vaccines. Intense campaigning in these regions will accrue a foundation of early adopters. Expansion of the advertising campaign, along with the foundation of early adopters, will lead the early majority to join Live Free. Once membership reaches a threshold level, the vast majority of new parents will follow the behavior of others by joining Live Free (55). The threshold level is the point at which the benefit of joining is greater than the cost of joining for a given individual (55). Cost and benefit of joining Live Free can be seen in terms of the social acceptability of doing so. Joining before others is a risk because the social acceptability of Live Free is not yet established. On the other hand, once Live Free is established as a social norm, individuals benefit from joining by partaking in socially acceptable behavior. Once a certain number of people join Live Free, meaning the threshold is met, the benefit is greater than the cost of joining and the majority of new parents will join. While starting Live Free will require intense advertising and specific targeting of early adopters, less intense advertising will be necessary once membership reaches the threshold level.

Live Free serves as a social network for new parents after recruitment through diffusion of innovations. A social network consists of a group or groups of people that develop a pattern of contacts or connections (56). Behavior and other phenomena spread through social networks using connections between individuals (57-58). As early adopters into Live Free are parents who accept the importance of vaccination, and as vaccinating one’s children is a part of membership, adherence to immunization will spread from early adopters to the majority through connections in this social network.

Live Free acknowledges that individuals’ behavior occurs in a broader context and that context shapes behavior. Enlisting Diffusion of Innovations Theory and Social Network Theory as group-level models to change behavior takes advantage of societal influences by changing the behavior of the entire group at the same time, instead of targeting each individual. Changing the behavior of the group also changes the context in which parents’ make decisions regarding vaccination. In this way, Live Free harnesses the ability of societal trends to change the behavior of an entire group and uses it to achieve nationwide childhood vaccination coverage.

REFERENCES

1. Every Child By Two. The Birth of ECBT. Washington, DC: Every Child By Two. http://www.ecbt.org/aboutecbt/.

2. Centers for Disease Control and Prevention. Measles – United States, 1992. Morbidity and Mortality Weekly Report 1993; 42(19):378-381.

3. Rosenstock IM. Why people use health services. Milbank Memorial Fund Quarterly 1966; 44(3):94-127.

4. Edberg M. Essentials of Health Behavior: Social and Behavioral Theory in Public Health. Sudbury, MA: Jones and Bartlett Publishers, 2007.

5. Salazar MK. Comparison of four behavioral theories. AAOHN Journal 1991; 39:128-135.

6. Ariely D. Predictably Irrational. New York: Harper Perennial, 2010.

7. Every Child By Two. Every Child By Two. Washington, DC: Every Child By Two. http://www.ecbt.org/index.cfm.

8. DeMartino B, Kumaran D, Seymour B, Dolan RF. Frames, biases, and rational decision-making in the human brain. Science 2006; 313:684-687.

9. Ariely D, Loewenstein G. The heat of the moment: The effect of sexual arousal on sexual decision making. Journal of Behavioral Decision Making 2006; 19:87-98.

10. Shin J, Ariely D. Keeping doors open: The effect of unavailability on incentives to keep options viable. Management Science 2004; 50(5): 575-586.

11. West R, Sohal T. “Catastrophic” pathways to smoking cessation: Findings from national survey. BMJ 2006; 332(7539):458-460.

12. Chong D, Druckman JN. Framing Theory. Annual Review of Political Science 2007; 10:103-126.

13. Ryan C. Prime time activism: Media strategies for grassroots organizing. Boston, MA: South End Press, 1991.

14. Evans WD, Hastings G. Public health branding: Recognition, promise, and delivery of healthy lifestyles (pp. 3-24). In: Evans WD, Hastings G, eds. Public Health Branding: Applying Marketing for Social Change. Oxford: Oxford University Press, 2008.

15. Siegel M, Doner L. Marketing Public Health: Strategies to Promote Social Change. Sudbury, MA: Jones and Bartlett Publishers, 2004.

16. Hicks JJ. The strategy behind Florida’s “truth” campaign. Tobacco Control 2001; 10:3-5.

17. Fishbein M, Hall-Jamieson K, Zimmer E, von Haeften I, Nabi R. Avoiding the boomerang: Testing the relative effectiveness of antidrug public service announcements before a national campaign. American Journal of Public Health 2002; 92(2):238-245.

18. Every Child By Two. Parents. Washington, DC: Every Child By Two. http://www.ecbt.org/parents/.

19. Hiltabiddle, SJ. Adolescent condom use, the health belief model, and the prevention of sexually transmitted disease. JOGNN 1996; 25(1): 61-66.

20. Austin LT, Ahmad F, McNally MJ, Stewart DE. Breast and cervical cancer screening in Hispanic women: A literature review using the health belief model. Women’s Health Issues 2002; 12(3):122-128.

21. Wiehe S, Garrison M, Christakis D, Ebel B, Rivara F. A systematic review of school-based smoking prevention trials with long-term follow-up. Journal of Adolescent Health 2005; 36(3):162-169.

22. Wardle J, Rapoport L, Miles A, Afuape T, Duman M. Mass education for obesity prevention: The penetration of the BBC’s ‘fighting fat, fighting fit’ campaign. Health Education Research 2002; 16(3):343-355.

23. Rosenstock IM, Strecher VJ, Becker MH. The health belief model and HIV risk behavior change (pp. 5-24). In: DiClemente RJ, Peterson JL, eds. Preventing AIDS: Theories and Methods of Behavioral Interventions. New York: Plenum Press, 1994.

24. Witte K, Stokols D, Ituarte P, Schneider M. Testing the health belief model in a field study to promote bicycle safety helmets. Communication Research 1993; 20(4):564-586.

25. Centers for Disease Control and Prevention. Health, United States, 2010: With special feature on death and dying. Hyattsville, MD: National Center for Health Statistics, 2011.

26. Knight JM, Kirincich AN, Farmer ER, Hood AF. Awareness of the risks of tanning lamps does not influence behavior among college students. Archives of Dermatology 2002; 138(10):1311-1315.

27. Morrison DM, Baker SA, Gillmore MR. Sexual risk behavior, knowledge, and condom use among adolescents in juvenile detention. Journal of Youth and Adolescence 1994; 23(2):271-288.

28. Hewleg-Larsen M, Tobias M, Cerban B. Risk perception and moralization among smokers in the USA and Denmark: A qualitative approach. British Journal of Health Psychology 2010; 15(4):871-886.

29. Tversky A, Simonson I. Context-dependent preferences. Management Science 1993; 39(10):1179-1189.

30. Tversky A, Kahneman D. The framing of decisions and the psychology of choice. Science 1981; 211(4481):453-458.

31. Stokols D. Translating social ecological theory into guidelines for community health promotion. American Journal of Health Promotion 1996; 10(4):282-298.

32. Balch G, Loughrey K, Weinberg L, Lurie D, Eisner E. Probing consumer benefits and barriers for the national 5 a day campaign: Focus group findings. Journal of Nutrition Education 1997; 29(4):178-183.

33. Hauser D. Five Years of Abstinence-Only-Until-Marriage (Assessing the Impact). Washington, DC: Advocates for Youth, 2004.

34. Thomas LW. A critical feminist perspective of the health belief model: Implications for nursing theory, research, practice, and education. Journal of Professional Nursing 1995; 11:246-252.

35. Every Child By Two. Vaccine Safety. Washington, DC: Every Child By Two. http://vaccinesafety.ecbt.org/ecbt/vaccinesafety.htm.

36. Georgetown University. Messaging 101: Create compelling messages. Georgetown University Center for Children and Families. http://ccf.georgetown.edu/index/tip-sheets.

37. Gust DA, Strine TW, Maurice E, Smith P, Yusuf H, Wilkinson M, Battaglia M, Wright R, Schwartz B. Underimmunization among children: Effects of vaccine safety concerns on immunization status. Pediatrics 2004; 114(1):16-22.

38. Sherif M. The Psychology of Social Norms. Oxford: Harper, 1936.

39. Elster J. Social norms and economic theory. Journal of Economic Perspectives 1989; 3(4):99-117.

40. Wakefield A et al. RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive development disorder in children. The Lancet 1998; 351(9103):637-641.

41. Burgess D, Burgess M, Leask J. The MMR vaccination and autism controversy in United Kingdom 1998-2005: Inevitable community outrage or a failure of risk communication? Vaccine 2006; 24(18):3921-3928.

42. Madsen KM et al. A population-based study of measles, mumps, and rubella vaccination and autism. NEJM 2002; 347(19):1477-1482.

43. Martin JA, Hamilton BE, Sutton PD, Ventura SJ, Mathews TJ, Osterman MJK. Births: Final data for 2008. National Vital Statistics Reports 2010; 59. Hyattsville, MD: National Center for Health Statistics, 2010.

44. Centers for Disease Control and Prevention. National Immunization Survey – Children. Atlanta, GA: Centers for Disease Control and Prevention, 2009.

45. Barclay L, Everitt L, Rogan F, Schmied V, Wyllie A. Becoming a mother – an analysis of women’s experience of early motherhood. Journal of Advanced Nursing 1997; 25:719-728.

46. Thonrton A, Young-DeMarco L. Four decades of trends in attitudes toward family issues in the United States: The 1960s through the 1990s. Journal of Marriage and Family 2001; 63(4):1009-1037.

47. Festinger L. A Theory of Cognitive Dissonance. Stanford, CA: Stanford University Press, 1957.

48. Aarts H, Dijksterhuis A, Custers R. Automatic normative behavior in environments: The moderating role of conformity in activating situational norms. Social Cognition 2003; 21(6):447-464.

49. Cohen DA, Scribner RA, Farley TA. A structural model of health behavior: A pragmatic approach to explain and influence health behaviors at the population level. Preventive Medicine 2000; 30(2):146-154.

50. Brehm J, Cohen A. Explorations in Cognitive Dissonance. Hoboken, NJ: John Wiley & Sons, 1962.

51. Elliot A, Devine P. On the motivational nature of cognitive dissonance: Dissonance as psychological discomfort. Journal of Personality and Social Psychology 1994; 67(3):382-394.

52. Aronson E. The theory of cognitive dissonance: A current perspective (pp. 2-34). In: Berkowitz L, ed. Advances in experimental social psychology (vol. 4). New York: Academic Press, 1969.

53. Andreasen A. Marketing Social Change: Changing Behavior to Promote Health, Social Development, and the Environment. San Francisco, CA: Jossey-Bass Publishers, 1995.

54. Ryan B, Gross NC. The diffusion of hybrid seed corn in two Iowa communities. Rural Sociology 1943; 8(1):15-24.

55. Granovetter M. Threshold models of collective behavior. American Journal of Sociology 1978; 83(6):1420-1443.

56. Newman M. The structure and function of complex networks. Society for Industrial and Applied Mathematics 2003; 45(2):167-256.

57. Bearman P, Moody J, Stovel K. Chains of affection: The structure of adolescent romantic and sexual networks. American Journal of Sociology 2004; 110(1):44-91.

58. Christakis NA, Fowler JH. The spread of obesity in a large social network over 32 years. NEJM 2007; 357(4):370-379.