OBJECTIVE: Increasing numbers of parents use alternative vaccination schedules that differ from the recommended childhood vaccination schedule for their children. We sought to describe national patterns of alternative vaccination schedule use and the potential “malleability” of parents' current vaccination schedule choices.
METHODS: We performed a cross-sectional, Internet-based survey of a nationally representative sample of parents of children 6 months to 6 years of age. Bivariate and multivariate analyses determined associations between demographic and attitudinal factors and alternative vaccination schedule use.
RESULTS: The response rate was 61% (N = 748). Of the 13% of parents who reported following an alternative vaccination schedule, most refused only certain vaccines (53%) and/or delayed some vaccines until the child was older (55%). Only 17% reported refusing all vaccines. In multivariate models, nonblack race and not having a regular health care provider for the child were the only factors significantly associated with higher odds of using an alternative schedule. A large proportion of alternative vaccinators (30%) reported having initially followed the recommended vaccination schedule. Among parents following the recommended vaccination schedule, 28% thought that delaying vaccine doses was safer than the schedule they used, and 22% disagreed that the best vaccination schedule to follow was the one recommended by vaccination experts.
CONCLUSIONS: More than 1 of 10 parents of young children currently use an alternative vaccination schedule. In addition, a large proportion of parents currently following the recommended schedule seem to be “at risk” for switching to an alternative schedule.
WHAT'S KNOWN ON THIS SUBJECT:
Increasing numbers of parents are following alternative vaccination schedules that differ from the recommended vaccination schedule for their young children. Following an alternative schedule leads to undervaccination and increases the risk of contracting vaccine-preventable diseases.
WHAT THIS STUDY ADDS:
This is one of the first studies to detail alternative vaccination schedule use among parents of young children nationally and to delineate the “malleability” of parent's attitudes regarding their vaccination schedule choices.
Despite well-documented health benefits of routine childhood immunization, the past 2 decades have seen marked increases in the numbers of parents with concerns about the safety, necessity, and benefits of recommended vaccines.1,–,3 For many parents, these concerns result in the adoption of an alternative vaccination schedule that differs from the childhood vaccination schedule recommended by the Centers for Disease Control and Prevention (CDC) for their children. Use of alternative vaccination schedules leads to underimmunization and has been shown to increase significantly the risk of contracting and spreading vaccine-preventable diseases (VPDs).1,4,–,7
Previous research identified attitudes such as concerns about vaccine safety, efficacy, and necessity, distrust of the motivation of vaccine advocates, and lack of enough information about vaccines to make an informed decision as being associated with use of an alternative schedule.2,4,8,–,17 The relative frequency with which parents use various types of alternative vaccination schedules and the “malleability” of those schedule choices (eg, how many parents have changed, or might change in the future, from the recommended schedule to an alternative vaccination schedule, or vice versa) have not yet been described, however. The latter information is particularly important as we assess the value of educational programs for vaccine-hesitant parents. To address these knowledge gaps, we surveyed a nationally representative sample of parents of young children regarding their use of and views about alternative vaccination schedules.
In May 2010, we conducted a cross-sectional study of a nationally representative population of parents of young children. This article focuses on responses to items related to alternative vaccination schedules. These questions were provided exclusively to the subsample of respondents who indicated that they were the parents, stepparents, or guardians of children 6 months to 6 years of age. The study was approved by the University of Michigan institutional review board.
The survey was conducted by using the Internet-enabled KnowledgePanel (Knowledge Networks, Palo Alto, CA), a probability-based panel designed to be representative of the US population. Initially, participants are chosen scientifically through random selection of telephone numbers and residential addresses. Persons in selected households are then invited by telephone or by mail to participate in the KnowledgePanel. For those who agree to participate but do not already have Internet access, Knowledge Networks provides a laptop and Internet connection at no cost. People who already have computers and Internet service are permitted to participate by using their own equipment. Each month, panelists are sent e-mails inviting them to participate in research. The KnowledgePanel has served as the sampling frame for other peer-reviewed studies on health topics related to children.18,–,22
Survey Measure of Use of Alternative Schedules
A primary outcome assessed in the survey was parents' report of using an alternative vaccination schedule for their young children. To identify this outcome, parents were provided with a brief description of the recommended schedule, as follows. “Most doctors provide childhood vaccines (shots) according to a schedule recommended by the Centers for Disease Control and Prevention and major organizations of doctors. That schedule (the ‘CDC vaccination schedule’) specifies the ages at which children should receive different vaccines.” Parents then were asked, “Does your child get all of the recommended vaccines at the specific ages outlined by the CDC vaccination schedule?” Parents who responded “no” to this question were identified as parents who followed an alternative vaccination schedule. Parents who indicated that they followed an alternative schedule were asked a series of closed-ended questions regarding details about the schedule they used, specifically, which vaccines were delayed, which vaccines were skipped altogether, who recommended using an alternative schedule, and whether an alternative schedule had always been followed for the child.
Attitudes About Alternative Schedules
Attitudes about alternative vaccination schedules were assessed for all parents of young children, regardless of the type of schedule they used. Attitudes were assessed by using a 4-point Likert scale (strongly disagree to strongly agree), which was dichotomized in some analyses (agree/strongly agree versus disagree/strongly disagree) to improve statistical power.
Survey Measures of Demographic Characteristics
Parents' age, gender, race/ethnicity, and level of education were provided by the survey vendor. Children's insurance status was based on parents' reports by using an item adapted from the National Health Interview Survey,23 and results were grouped into 3 categories, namely, public (State Children's Health Insurance Program, Medicaid, and/or Medicare), private, or other/no insurance. Race/ethnicity was provided by the survey vendor in 5 mutually exclusive categories (non-Hispanic white, non-Hispanic black, non-Hispanic other, ≥2 races, or Hispanic). For our analyses, non-Hispanic other and ≥2 races were combined into 1 category, because of small numbers of respondents in those categories.
Descriptive statistics were generated for each variable. Bivariate associations were assessed by using Pearson's χ2 tests and bivariate logistic regression. Independent predictors of alternative vaccination schedule use were assessed by using a multivariate logistic regression model that controlled for parent's race and income, child's insurance, and whether the child had a regular health care provider. Those variables were selected because of our a priori hypothesis that they would be associated with alternative vaccination schedule use (race/ethnicity, income, and insurance) or because they were significantly associated with this outcome (P ≤ .05) in bivariate analyses (child had a regular health care provider). For derivation of national estimates, all results incorporated probability sampling weights provided by the survey vendor. All proportions presented in this article are weighted proportions. Analyses were performed by using Stata 10 (Stata Corp, College Station, TX).
The overall survey response rate was 61%; there were 2064 respondents, including 1460 parents with children younger than 18 years in the household, of whom 771 indicated they had ≥1 child aged 6 months to 6 years of age. Characteristics of those parents are presented in Table 1. Briefly, the majority of the parents in this sample were white (63%), were women (57%), and were between 30 of 44 years of age (55%). Most parents (95%) reported that their children had a regular health care provider. The majority of parents had >1 child in the household (73%) and had a “young child” who was older than 1 year (91%).
Use of Alternative Vaccination Schedules
Among parents of young children, 13% reported using some type of alternative vaccination schedule (“alternative vaccinators”), in keeping with previous studies.10 Although our definition of alternative schedule use was broad (and therefore might misclassify parents as alternative vaccinators if they missed appointments or experienced a supply shortage), the internal consistency of our results suggests that this did not occur frequently. For example, the vast majority of parents who were identified as alternative vaccinators had antivaccination attitudes (80%–95%, depending on the attitude statement), 65% of those parents indicated that they had followed an alternative vaccination plan for their other children, and very few parents (2% of parents overall and 17% of alternative vaccinators) reported refusing all vaccines for their young children. The most common forms of schedule alterations were refusing only certain vaccines completely and delaying some vaccines until the child was older (Table 2). The vast majority of alternatively vaccinating parents (>80%) had >1 schedule alteration.
Among the alternatively vaccinating parents (unweighted N = 60), only 8% reported using a well-known alternative schedule, such as those promoted by Dr William Sears24 (6% of alternative vaccinators) and Dr Donald Miller25 (2%). Instead, it was more common for alternative vaccinators to indicate that they themselves (41%) or a friend (15%) had developed the schedule. Among the 36% of respondents who endorsed the “other” response to this query, several indicated in the free-text section that they had “worked with their child's physician” to develop the alternative schedule.
Table 3 depicts the specific vaccines refused, delayed, or provided over a prolonged dosing interval among alternative vaccinators. H1N1 and seasonal influenza vaccine were the vaccines most commonly refused altogether (86% and 76%, respectively). The vaccines most commonly delayed to an age older than that recommended were the measles-mumps-rubella (26%) and varicella (46%) vaccines. The vaccines most commonly provided over an extended dosing period were the measles-mumps-rubella (45%) and diphtheria-tetanus-acellular pertussis (43%) vaccines.
Parents perceived varied levels of physician support for following an alternative vaccination schedule. Among alternative vaccinators, 8% indicated that they had to change providers because their child's doctor refused to go along with their vaccination preferences, 30% indicated that their child's doctor “seemed hesitant to go along” with their vaccination preferences but still agreed to do so, 40% indicated that their child's doctor “seemed supportive” of their vaccination preferences, and 22% indicated that their child's doctor had been the one to suggest using an alternative vaccination schedule. We did not collect information about why a child's doctor might have suggested such a schedule; it is possible, for example, that in some cases this was attributable to concurrent illness or vaccine shortages.
Among alternative vaccinators (unweighted N = 60), most (59%) indicated that they had always followed an alternative vaccination schedule for their young child. However, a large minority (30%) indicated that they had initially followed the recommended vaccination schedule but subsequently changed to an alternative schedule. In contrast, only 11% of alternatively vaccinating parents reported changing from an alternative schedule to the schedule recommended by the CDC. Among the parents who changed schedule type, the majority (61%) did so because it “seemed safer.” Less commonly, parents reported changing schedule type because they thought it would create less distress for their child (20%) or would be more effective (12%).
Factors Associated With Alternative Vaccination Use
In bivariate analyses, levels of use of any type of alternative vaccination schedule were significantly lower among black parents than among nonblack parents and were significantly higher among children who did not have a regular health care provider (Table 4). Alternative vaccination schedule use was not associated in bivariate analyses with child's age, gender, or insurance, parent's age, gender, insurance, education, or marital status, number of children living in the household, or parent-reported health status for the child.
In a multivariate model that controlled for child's insurance, parent's race/ethnicity and income, and whether the child had a regular health care provider (Table 4), only nonblack race and not having a regular health care provider for the child remained associated with higher odds of using an alternative vaccination schedule. The small sample size for alternative vaccinators prevented further stratification of the analyses according to the specific type of alternative vaccination schedule used.
Parents' Opinions About Alternative Schedules
All parents of young children, regardless of the type of vaccination schedule they followed, were queried about their attitudes regarding alternative vaccination schedules. As expected, there were significant differences in attitudes between parents who did versus did not follow an alternative vaccination schedule (Table 5). In general, parents who followed an alternative vaccination schedule were more likely than parents who did not to agree that an alternative schedule was safer, was associated with fewer adverse effects, and let parents skip unnecessary vaccines. Alternative vaccinators were less likely than parents following the recommended schedule to think that alternative schedules increased the risk of contracting and spreading disease.
A notable finding from this analysis was the large proportion of parents following the recommended schedule who held beliefs that seemed counter to this practice. For example, nearly 1 of 4 parents (22%) following the recommended schedule disagreed or strongly disagreed that the schedule “recommended by vaccination experts” was the best one to follow. Similarly, 1 of 5 parents who followed the recommended vaccination schedule thought that delaying vaccine doses was safer than providing them according to the recommended schedule (Table 5).
In bivariate analyses, a history of alternative schedule use was consistently associated with nonmainstream beliefs about vaccination. Such beliefs also tended to be more common among parents whose children did not have a regular health care provider and those with higher incomes, although this was not consistent across all attitude questions (Table 6).
To determine independent predictors of each attitude, we used a series of 9 multivariate models that were each adjusted for parent's income and race/ethnicity, child's insurance, whether the child had a regular health care provider, and whether the parent reported following an alternative vaccination schedule. For each of the 9 attitude statements, following an alternative vaccination schedule was the only variable that remained associated with the vaccination attitude in the multivariate model (95% confidence intervals were 7.26–26.11, depending on the attitude assessed).
At the national level, we found that >1 of 10 parents reported following a vaccination schedule other than that recommended by the CDC for their young children. Consistent with previous reports,2,5,10,17 refusal of all vaccines was relatively uncommon in our study (2% of parents overall). Instead, alternative vaccinators tended to delay or skip only certain vaccines.
Skipping or delaying even a subset of recommended vaccines was shown previously to be associated with significantly increased risk of contracting and spreading VPDs. For example, Feikin et al6 demonstrated that children whose parents had opted out of ≥1 recommended vaccine were 22 times more likely than fully vaccinated children to contract measles and nearly 6 times more likely to contract pertussis. Even fully vaccinated individuals are at increased risk of VPDs if they reside in a community with a large proportion of underimmunized individuals. For example, a study from Colorado demonstrated that, for every 1% increase in the proportion of school-aged children who were underimmunized, the risk of pertussis infection among fully vaccinated children doubled.7
Importantly, and unlike previous research on this topic, we found that using an alternative vaccination schedule was most strongly associated with not having a regular health care provider for the child. This finding is not surprising, because a strong physician recommendation for vaccination has been shown to be a consistent predictor of vaccine utilization.10,12,16,26 What is not clear, however, is which phenomenon occurs first. Do parents who follow an alternative schedule have a difficult time finding a physician for their child who supports their vaccination beliefs, or are parents who tend not to engage in regular health care for their children those who also tend to follow an alternative vaccination schedule? Our study suggests that most parents who wish to follow an alternative vaccination schedule are able to access physicians who will support their beliefs; only 8% of the alternatively vaccinating parents in our sample reported having to change providers to maintain the vaccination schedule they wanted. An alternative explanation is that some parents who were identified as alternative vaccinators in our study might actually believe strongly in vaccination but, because of difficulty accessing medical care (eg, because they lacked a regular provider), missed or delayed doses. How alternative vaccinators interact with the primary care health system should be an important question for future research if effective outreach activities to increase vaccination rates are to be developed.
Our results differed from previous studies in that we did not find associations between alternative vaccination schedule use and most of the child-, parent-, and family-related demographic factors assessed (with the exception of black race). This divergence is likely attributable, in part, to differences in how alternative schedules are defined. We defined alternative vaccination schedules on the basis of any alterations from the schedule recommended by the CDC. Other studies used somewhat different alternative schedule outcomes, such as receiving no vaccines17 or not being up to date with vaccines by a certain age,9,27 or made comparisons between those who delayed/refused vaccines and those who “had doubts” but still underwent vaccination.10 Because of the broad way in which we defined alternative schedules in our study, some parents who skipped or delayed a vaccine dose because of vaccine shortages, illness, or missed appointments might have been classified erroneously as alternative vaccinators. It is possible that these subtle differences in methods used and outcomes assessed could explain why our results differ from those of others. In general, however, our results on the prevalence of alternative vaccinators are in keeping with previous reports,10 which suggest that any misclassification of parents in our study was minimal. Furthermore, because most of the previous surveys were performed several years ago, they might have captured a time when alternative vaccination schedule use was more limited to specific subpopulations. Recent work suggests that vaccine safety concerns and refusals occur at similar levels across subpopulations defined on the basis of various demographic characteristics and generally are increasing overall.2
A concerning finding from our study was the large proportion of parents currently following the recommended schedule who seemed to be “at risk” for changing to an alternative vaccination schedule. One of 5 parents who followed the recommended schedule agreed that delaying vaccine doses was safer than the recommended schedule, and nearly 1 of 4 of these parents disagreed that the best vaccination schedule to follow was the one recommended by vaccination experts. The additional finding that nearly one-third of the alternatively vaccinating parents in our study had initially followed the recommended vaccination schedule for their children supports this concern. These findings highlight the need to develop strategies quickly to prevent the spread of attitudes and beliefs that counter vaccination. Fortunately, previous work suggested that many parents who are “on the fence” about vaccination have views that might be modifiable through targeted educational approaches.8,28,–,30
An intriguing finding from our study was that a large proportion of alternative vaccinators agreed that undervaccination of children increases the risk of infection and spread of disease. This seeming contradiction between beliefs and actions suggests that those parents may not think that their children are individually at increased risk of VPDs as a result of following an alternative schedule, and it points to a potentially important educational target. Perceived risk of infection was shown to be a significant predictor of vaccination across a wide range of studies,13 but changing risk perceptions among those parents is not likely to be easy.31 Additional work is needed to understand how best to present risks to parents in a way that is both compelling and personal. Targeting educational messages to each individual parent's personal beliefs, experiences, and concerns is one approach that shows promise in this regard.28,–,30
Our results should be interpreted in light of several limitations. First, as with any survey-based research, sample biases might have affected our results. Participants were registered panelists recruited by a survey research firm and therefore might have had inherently greater interest in study participation or might have differed from the general population with respect to education or baseline health status. Second, Internet-based surveys have the potential to represent certain populations inadequately. In this study, underrepresented minorities were purposely oversampled during panel recruitment, and Internet access and software were provided to participants as needed. The survey sampling methods used in this study were validated previously as being able to provide nationally representative samples with respect to race, ethnicity, and a variety of other sociodemographic variables.32,–,34 Finally, despite a large overall sample size, the sample sizes for specific types of vaccination schedule alterations (eg, delay or skip) were relatively small, which prevented us from being able to differentiate predictor variables according to specific schedule type.
In one of the first national studies to detail parents' use of alternative vaccination schedules for their young children, we found that nearly 1 of 10 parents reported using a vaccination schedule other than that recommended by the CDC. A surprising finding was that a large proportion of parents currently following the recommended schedule seemed have attitudes counter to this practice, which suggests that they may be at risk for switching to an alternative schedule in the future. The results of this study highlight the need to develop interventions quickly to quell the apparently growing concerns among parents about the safety and necessity of recommended childhood vaccines.
This research was conducted as part of the C. S. Mott Children's Hospital National Poll on Children's Health. The project was funded by the Clinical Sciences Scholars Program at the University of Michigan.
- Accepted June 30, 2011.
- Address correspondence to Amanda F. Dempsey, MD, PhD, MPH, Child Health Evaluation and Research Unit, University of Michigan, 300 N Ingalls St, Room 6E08, Ann Arbor, MI 48109-5456. E-mail:
FINANCIAL DISCLOSURE: Dr Dempsey receives compensation for service on an advisory board for Merck related to male human papillomavirus vaccination; the company had no input into the design, implementation, analysis, or presentation of the results of this study, and Dr Dempsey receives no research support from Merck. The other authors have indicated they have no financial relationships relevant to this article to disclose.
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- Copyright © 2011 by the American Academy of Pediatrics