Previsit Screening for Parental Vaccine Hesitancy: A Cluster Randomized Trial

Frequency of vaccine hesitancy among patients with advanced cancer

BACKGROUND

Vaccine hesitancy has become prevalent in society. Vulnerable populations, such as those with cancer, are susceptible to increased morbidity and mortality from diseases that may have been prevented through vaccination.

OBJECTIVES

Our objective was to determine patient perception of vaccine efficacy and safety and sources of information that influence decisions.

METHODS

This study was a prospective cross-sectional survey trial conducted from March 10, 2022, to November 1, 2022, at a Supportive Care Clinic. Patients completed the survey with a research assistant or from a survey link. Vaccine hesitancy was defined as a response of 2 or more on the Parent Attitudes About Childhood Vaccines (PACV-4). Perception on vaccine safety and efficacy along with the importance of sources of information were determined by a questionnaire.

RESULTS

Of the 72 patients who completed the PACV-4, 30 were considered vaccine-hesitant (42%). Of those who completed the survey alone (35), 23 (66%) were vaccine-hesitant; and of those who completed the survey with the help of a study coordinator (37), 7 (19%) were vaccine-hesitant. The most important source for decision-making was their doctor (82%, 95% CI 73-89), followed by family (42%, 95% CI 32-52), news/media (31%, 95% CI 22-41), and social media (9%, 95% CI 4-16). Clinical and demographic factors including age, gender, race/ethnicity, education level, and location of residence were not associated with vaccine hesitancy.

SIGNIFICANCE OF RESULTS

Vaccine hesitancy is present among patients with advanced cancer. The high value given to the doctor's recommendation suggests that universal precautions regarding vaccine recommendation may be an effective intervention.

Influenza Vaccine Hesitancy: Scope, Influencing Factors, and Strategic Interventions

Influenza vaccination rates in children are suboptimal. One underlying reason is influenza vaccine hesitancy. Tools such as the Parent Attitudes about Childhood Vaccines survey and the Vaccine Hesitancy Scale can be used to measure influenza vaccine hesitancy. The adapted Increasing Vaccination Model from Brewer and colleagues can help identify factors that influence influenza vaccine hesitancy, motivation, and uptake. Several strategies can be used to address influenza vaccine hesitancy, which we discuss further in this review.

Sometimes Your Heart Says 'I Don't Know': Insights From Parents of Undervaccinated Children

STUDY OBJECTIVE

To explore drivers of suboptimal vaccination rates by understanding why parents without strong antivaccine beliefs do not fully vaccinate their children.

METHODS

Four focus groups were conducted in Washington state with 41 parents of children aged 24 to 48 months who delayed, declined, or missed some but not all vaccines. During the focus groups, parents were asked about reasons their child was undervaccinated, information that might address their concerns, and additional support they needed. Transcripts were analyzed using template analysis with deductive and inductive codes.

RESULTS

Focus groups identified multiple reasons for parents deciding to delay or decline vaccines for their children, including issues of individualism and control. The groups emphasized the impact of personal circumstances, such as changes in insurance, on whether children were vaccinated. Our data also shed light on the reasons that parents do vaccinate their children, including school vaccination requirements, negative experiences with vaccine-preventable diseases, and a family tradition of vaccinating. Focus group participants offered suggestions for improving vaccine communication with parents such as having more parent/patient-friendly vaccine information, providing forums to discuss their concerns, and offering vaccination information in advance of well-child appointments.

CONCLUSIONS

To achieve the full benefit of vaccines on individual and community health, we need better ways to address vaccine hesitancy and decrease barriers. We suggest that many hesitant parents would benefit from more dialog with health care providers about vaccines, more approachable educational materials, and enforcement of existing policies requiring vaccines in schools and childcare facilities.

Rural parents' attitudes and beliefs on the COVID-19 pediatric vaccine: An explanatory study

The coronavirus disease 2019 (COVID-19) first came to the Unites States in January 2020. Though adult and pediatric vaccines became available to the public, vaccine uptake among youth and particularly younger children has been gradual. This explanatory study aimed to better understand parents' attitudes and beliefs of the pediatric COVID-19 vaccine and the barriers and facilitators to vaccine uptake in a rural community through a brief, online demographic survey, and in-depth qualitative interviews. Forty-one in depth interviews were conducted with parents (31-English and 10-Spanish-speaking) residing in rural and frontier counties in Colorado between September 2021 and February 2022. Six emergent themes related to COVID-19 pediatric vaccine uptake were identified among the population. These themes spanned the three levels of influence in the Social Ecological Model (individual, interpersonal, and community levels). The six themes were identified as such; 1) Vaccine accessibility was associated with pediatric COVID vaccine uptake in rural communities, 2) Previous pediatric vaccine behaviors were not associated with COVID-19 pediatric vaccine uptake, 3) Perceived health status of a child or family member influenced pediatric COVID-19 vaccine uptake, 4) COVID-19 health seeking behaviors, like COVID pediatric vaccine uptake, are influenced by an individual's prosocial or individualistic perspectives, 5) Child autonomy and "age of consent" frames vaccine decision making behaviors in parents, and lastly 6) Social networks impacted COVID-19 pediatric vaccine decision making. These findings inform next steps for COVID-19 pediatric vaccine uptake including targeted and tailored messaging for communities (cues to actions), engaging youth stakeholders, and identifying trusted sources to build rapport and trust between health professionals and community members. The growing vaccine hesitancy among parents has serious implications for disease eradication and future viral outbreaks. Understanding the perceived barriers and facilitators to pediatric vaccine uptake is important to maintain the health of our youth and communities.

A systematic literature review to clarify the concept of vaccine hesitancy

Vaccine hesitancy (VH) is considered a top-10 global health threat. The concept of VH has been described and applied inconsistently. This systematic review aims to clarify VH by analysing how it is operationalized. We searched PubMed, Embase and PsycINFO databases on 14 January 2022. We selected 422 studies containing operationalizations of VH for inclusion. One limitation is that studies of lower quality were not excluded. Our qualitative analysis reveals that VH is conceptualized as involving (1) cognitions or affect, (2) behaviour and (3) decision making. A wide variety of methods have been used to measure VH. Our findings indicate the varied and confusing use of the term VH, leading to an impracticable concept. We propose that VH should be defined as a state of indecisiveness regarding a vaccination decision.

Parent Attitudes Towards Childhood Vaccines After the Onset of SARS-CoV-2 in the United States

OBJECTIVE

To understand the influence of a novel infectious disease epidemic on parent general attitudes about childhood vaccines.

METHODS

We conducted a natural experiment utilizing cross-sectional survey data from parents of infants in Washington and Colorado participating in a larger trial that began on September 27, 2019. At enrollment, parents completed the short version of the Parental Attitudes about Childhood Vaccines (PACV-SF), a validated survey scored from 0 to 4, with higher scores representing more negative attitudes. The exposure variable was onset of the SARS-CoV-2 pandemic in the United States, with the before-period defined as September 27, 2019 to February 28, 2020 and the after-period defined as April 1, 2020-December 10, 2020, with the after-period further separated into proximate (April 1, 2020-July 31, 2020) and distant periods (August 1, 2020-December 10, 2020). The outcome variable was parent negative attitudes about childhood vaccines, defined as a score of ≥2 on the PACV-SF. We estimated the probability of the outcome after (vs before) the exposure using log-binomial regression with generalized estimating equations adjusted for demographic confounding variables.

RESULTS

Among 4562 parents, the risk of negative attitudes was lower immediately after (vs before) SARS-CoV-2 onset (adjusted risk ratio [aRR] = 0.58; 95% confidence interval [CI], 0.36, 0.94; P = .027), but by August-December 2020, the average rate of negative attitudes was 35% higher than during April-July 2020 (aRR: 1.35; 95% CI: 1.13, 1.61; P = .0009).

CONCLUSIONS

A reduced risk of negative general vaccine attitudes observed immediately after SARS-CoV-2 onset was quickly attenuated.

Belief correlations with parental vaccine hesitancy: Results from a national survey

We conducted a nationally representative survey of parents’ beliefs and self‐reported behaviors regarding childhood vaccinations. Using Bayesian selection among multivariate models, we found that beliefs, even those without any vaccine or health content, predicted vaccine‐hesitant behaviors better than demographics, social network effects, or scientific reasoning. The multivariate structure of beliefs combined many types of ideation that included concerns about both conspiracies and side effects. Although they are not strongly related to vaccine‐hesitant behavior, demographics were key predictors of beliefs. Our results support some of the previously proposed pro‐vaccination messaging strategies and suggest some new strategies not previously considered.

Seroconversion rate after vaccination against COVID-19 in patients with cancer-a systematic review

BACKGROUND

Coronavirus disease 2019 (COVID-19) has affected >210 million people worldwide. An optimal therapeutic approach for COVID-19 remains uncertain, to date. Since the history of cancer was linked to higher mortality rates due to COVID-19, the establishment of a safe and effective vaccine coverage is crucial in these patients. However, patients with cancer (PsC) were mostly excluded from vaccine candidates' clinical trials. This systematic review aims to investigate the current available evidence about the immunogenicity of COVID-19 vaccines in PsC.

PATIENTS AND METHODS

All prospective studies that evaluated the safety and efficacy of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were included, with immunogenicity after the first and the second dose as the primary endpoint, when available.

RESULTS

Vaccination against COVID-19 for PsC seems overall safe and immunogenic after well-conducted vaccination schedules. Yet the seroconversion rate remains lower, lagged or both compared to the general population. Patients with hematologic malignancies, especially those receiving B-cell-depleting agents in the past 12 months, are the most at risk of poor seroconversion.

CONCLUSION

A tailored approach to vaccination may be proposed to PsC, especially on the basis of the type of malignancy and of the specific oncologic treatments received.

Parental vaccine hesitancy: scope, causes, and potential responses

PURPOSE OF REVIEW

We reviewed the literature about parental vaccine hesitancy, focusing on publications from October 2019 to April 2021 to describe patterns and causes of hesitancy and interventions to address hesitancy.

RECENT FINDINGS

Recent studies expand understanding of the prevalence of vaccine hesitancy globally and highlight associated individual and contextual factors. Common concerns underlying hesitancy include uncertainty about the need for vaccination and questions about vaccine safety and efficacy. Sociodemographic factors associated with parental vaccine hesitancy vary across locations and contexts. Studies about psychology of hesitancy and how parents respond to interventions highlight the role of cognitive biases, personal values, and vaccination as a social contract or norm. Evidence-based strategies to address vaccine hesitancy include presumptive or announcement approaches to vaccine recommendations, motivational interviewing, and use of immunization delivery strategies like standing orders and reminder/recall programs. A smaller number of studies support use of social media and digital applications to improve vaccination intent. Strengthening school vaccine mandates can improve vaccination rates, but policy decisions must consider local context.

SUMMARY

Vaccine hesitancy remains a challenge for child health. Future work must include more interventional studies to address hesitancy and regular global surveillance of parental vaccine hesitancy and vaccine content on social media.

Vaccine hesitancy and reported non-vaccination in an Irish pediatric outpatient population

Vaccine hesitancy is defined as a delay in acceptance, or refusal, of vaccines, despite availability. It is a complex and context specific phenomenon and identified as a global health priority. The "Parent Attitudes about Childhood Vaccines" (PACV) questionnaire is a validated tool for identifying vaccine hesitancy. Our aim was to use the PACV to assess vaccine hesitancy and its relationship with reported non-vaccination in an Irish population, for the first time. Our participants were parents or caregivers of children attending general pediatric clinics in a tertiary pediatric hospital in Dublin, Ireland, between September and December 2018. In total, 436 participants completed the questionnaire. 5.5% of our population reported non-vaccination. Human papilloma virus and measles, mumps, rubella vaccines were the most commonly cited vaccines of concern (11.5% and 6.7%, respectively), and autism spectrum disorder was the most commonly side effect of concern (4.3%). Mean PACV score was 26.9 (SD 19.1), with a significant difference between non-vaccinators and vaccinators (53.2 vs 25.3, p<0.001). Safety and efficacy concerns were the major contributor to non-vaccination. 14.4% of our population were vaccine-hesitant using the conventional cut-off score, which increased to 22% when using an optimal cut-off which maximized sensitivity and specificity. The accuracy of the PACV score to identify non-vaccination was good (area under the ROC curve = 0.827), and the optimal cut-off had a high negative predictive value (98.5%).Conclusion: PACV identified reported non-vaccination with high accuracy in our population. It may be useful to screen vaccine-hesitant parents who could benefit from interventions to improve uptake. What is Known: • Vaccine hesitancy is a leading threat to global health, with falls in vaccine uptake associated with disease outbreaks worldwide. • The Parent Attitudes about Childhood Vaccines (PACV) questionnaire is a validated measure of vaccine hesitancy and correlates with non-vaccination in many populations. What is New: • This large study in a pediatric outpatient clinic setting represents the first use of the PACV in a Western European population to assess vaccination hesitancy. • The PACV may be an effective way of screening a pediatric clinic population to identify vaccine-hesitant parents or caregivers for targeted vaccine promotion.

The effect of screening for vaccine hesitancy on the subsequent development of hesitancy: a randomized controlled trial, Houston, TX

Vaccine hesitancy remains a global health threat. Addressing parental vaccine hesitancy is essential to maintaining high vaccine coverage levels and preventing disease outbreaks; however, it is unknown if administering a vaccine hesitancy screening tool negatively impacts parental vaccine beliefs. We conducted a stratified randomized controlled trial in pediatric primary care practices. English-speaking parents ≥18 years of age seeking routine care for infants <3 months of age were eligible. Participants were randomized to receive 1 of 2 surveys - the Parent Attitudes about Childhood Vaccines (PACV) survey or a placebo survey. Six months after initial enrollment, all participants were asked to complete the PACV, regardless of initial randomization group. Our primary outcome was the proportion of hesitant to non-hesitant parents at 6-months between randomization groups. We examined associations between vaccine hesitancy and participant characteristics. We also evaluated the change in the proportion of vaccine-hesitant parents in the PACV group between baseline and 6-month follow up. We enrolled 1705 parents at baseline. At 6-month follow up, 819 parents completed the PACV (50.2% from PACV group vs. 54.1% from placebo group). The proportion of hesitant parents at 6 months did not differ between PACV and placebo groups (6.6% vs. 6.1%; p = .78) and the odds of hesitancy among PACV group participants was not higher than those in the placebo group (OR = 1.10; 95% CI: 0.63-1.93; p = .743). Race was the only characteristic significantly associated with vaccine hesitancy at 6-month follow up (p = .003). Overall, administration of the PACV did not trigger vaccine hesitancy in this study population.

A systematic review and meta-analysis of effectiveness of decision aids for vaccination decision-making

BACKGROUND

This systematic review and meta-analysis aimed to assess the effectiveness of vaccination decision aids compared with usual care on vaccine uptake, vaccine attitudes, decisional conflict, intent to vaccinate and timeliness.

METHODS

Searches were conducted in OVID Medline, OVID Embase, CINAHL, PsycINFO, the Cochrane Library and SCOPUS. Randomised controlled trials were included if they evaluated the impact of decision aids as defined by the International Patient Decision Aids Standards Collaboration. Where possible, meta-analysis was undertaken. Where meta-analysis was not possible, we conducted a narrative synthesis. Risk of bias in included trials was assessed using the Cochrane Collaboration's risk of bias tool. Data were analysed using STATA.

RESULTS

Five RCTs were identified that evaluated the effectiveness of decision aids in the context of vaccination decision making. Meta-analysis of four studies showed that decision aids may have slightly increased vaccination uptake, but this was reduced to no effect once studies with higher risk of bias were excluded. Meta-analysis of three studies showed that decision aids moderately increased intention to vaccinate. Narrative synthesis of two studies suggested that decision aids reduced decisional conflict. One study reported that decision aids decreased perceived risk of vaccination. Content, format and delivery method of the decision aids varied across the studies. It was not clear from the information reported whether these variations affected the effectiveness of the decision aids.

CONCLUSION

Decision aids can assist in vaccine decision making. Future studies of decision aids could provide greater detail of the decision aids themselves, which would enable comparison of the effectiveness of different elements and formats. Standardising decision aids would also allow for easier comparison between decision aids.

Applied techniques for putting pre-visit planning in clinical practice to empower patient-centered care in the pandemic era: a systematic review and framework suggestion

Background

One of the main elements of patient-centered care is an enhancement of patient preparedness. Thus, pre-visit planning assessment tools was emerged to prepare and involve patients in their treatment process.

Objective

The main objective of this article was to review the applied tools and techniques for consideration of putting pre-visit planning into practice.

Methods

Web of Science, Scopus, IEEE, and PubMed databases were searched using keywords from January 2001 to November 2020. The review was completed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. Then, qualitative analysis was done to suggest an appropriate framework by mapping the main concepts.

Results

Out of 385 citations were retrieved in initial database searches, 49 studies from ten countries were included. Applied pre-visit techniques can be classified into eight categories. Our results showed that almost 81% of studies were related to procedures that were done between each visit, while 42% of articles were related to before visits. Accordingly, the main approach of included articles was patient preparedness. While 38 studies reported this approach is effective, three studies reported the effectiveness of such tools as moderate, only two articles believed it had a low effect on improving patient-centered care.

Conclusion

This survey summarized the characteristics of published studies on pre-visit planning in the proposed framework. This approach could enhance the quality of patient care alongside enhancement patient-provider communication. However, such an approach can also be helpful to control pandemic diseases by reducing unnecessary referrals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-021-06456-7.

What Is the State-of-the-Art in Clinical Trials on Vaccine Hesitancy 2015-2020?

BACKGROUND

Vaccine hesitancy is related to a delay in acceptance or refusal of vaccination.

AIM

to perform a systematic review of clinical trials on vaccine hesitancy (2015-2020).

METHODS

a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria (PRISMA). Five databases were screened-PubMed, Cochrane Library, DOAJ, SciELO and b-on-which comprise multiple resources.

KEYWORDS

"Vaccine hesitancy" and ("randomized controlled trial" or "clinical trial").

INCLUSION CRITERIA

trials about "vaccine hesitancy" enrolling patients and/or health professionals (2015-2020).

EXCLUSION CRITERIA

studies about other topics, repeated and qualitative studies, reviews and papers written in languages other than English, Portuguese, French or Spanish.

RESULTS

a total of 35 trials out of 90 were selected (19 PubMed, 14 Cochrane Library, 0 DOAJ, 0 SciELO and 2 b-on). Selected trials were classified into five topics: children/pediatric (n = 5); online or electronic information (n = 5); vaccination against a specific disease (n = 15) (e.g., influenza or COVID-2019); miscellaneous (n = 4); and educational strategies (n = 6).

CONCLUSION

the provision of online or electronic information (e.g., through virtual reality, social websites of experts, or apps), communication-based interventions and training of health professionals, residents or subjects seemed to improve vaccine hesitancy.

Vaccine Hesitancy: Characteristics of the Refusal of Childhood Vaccination in a Peruvian Population

Understanding the determinants of vaccine hesitancy is paramount to reinstate confidence in immunizations. The objective of this investigation was to explore the characteristics of the vaccination decision-making process that may result in the refusal of childhood immunization in Peru, during February-June 2020. A descriptive, cross-sectional study involving telephone interviews was executed in Peru. The Parents Attitudes about Childhood Vaccines (PACV) survey was used. A demographic analysis was done, followed by an unadjusted exploratory subgroup analysis. Out of 552 subjects, 9.8% were considered vaccine hesitant, 70.3% had purposively delayed vaccination, 88.4% thought fewer vaccines were better and 52.2% were concerned about vaccine safety. The level of hesitancy was inversely proportional to the level of education and the number of children at home. Mothers and subjects aged ≤29 years showed a greater level of vaccine hesitancy. This population displays a vaccine-hesitant conduct. Vaccine safety and the number of vaccines to administer are important determining factors. This behavior could be influenced by variables such as level of education, number of children at home, parental relationship, and age. These results help understand local vaccination behaviors. More studies are encouraged to confirm and validate these findings.

Mask usage, social distancing, racial, and gender correlates of COVID-19 vaccine intentions among adults in the US

Vaccine hesitancy could become a significant impediment to addressing the COVID-19 pandemic. The current study examined the prevalence of COVID-19 vaccine hesitancy and factors associated with vaccine intentions. A national panel survey by the National Opinion Research Center (NORC) was designed to be representative of the US household population. Sampled respondents were invited to complete the survey between May 14 and 18, 2020 in English or Spanish. 1,056 respondents completed the survey—942 via the web and 114 via telephone. The dependent variable was assessed by the item “If a vaccine against the coronavirus becomes available, do you plan to get vaccinated, or not?” Approximately half (53.6%) reported intending to be vaccinated, 16.7% did not intend, and 29.7% were unsure. In the adjusted stepwise multinominal logistic regression, Black and Hispanic respondents were significantly less likely to report intending to be vaccinated as were respondents who were females, younger, and those who were more politically conservative. Compared to those who reported positive vaccine intentions, respondents with negative vaccine intentions were significantly less likely to report that they engaged in the COVID-19 prevention behaviors of wearing masks (aOR = 0.53, CI = 0.37–0.76) and social distancing (aOR = 0.22, CI = 0.12–0.42). In a sub-analysis of reasons not to be vaccinated, significant race/ethnic differences were observed. This national survey indicated a modest level of COVID-19 vaccine intention. These data suggest that public health campaigns for vaccine uptake should assess in greater detail the vaccine concerns of Blacks, Hispanics, and women to tailor programs.

Beliefs about causes of autism and vaccine hesitancy among parents of children with autism spectrum disorder

Vaccine hesitancy may be more common among parents of children with autism spectrum disorder (ASD). We examined factors associated with ASD-specific vaccine hesitancy among caregivers of children with ASD who participated in the SPARK study (Simons Foundation Powering Autism Research for Knowledge). 225 participants completed an online survey containing the Parent Attitudes About Childhood Vaccines (PACV) questionnaire (measure of vaccine hesitancy) and the Illness Perception Questionnaire revised for parents of children with ASD (IPQ-R-ASD; measure of parents' views about ASD). 65 participants (28.8%) were vaccine hesitant (PACV score ≥ 50); children of vaccine-hesitant parents (VHPs) were less likely to be first born (n = 27, 41.5%), had greater ASD-symptom severity (mean Social Communication Questionnaire score = 23.9, SD = 6.9), and were more likely to have experienced developmental regression (n = 27, 50.9%) or plateau (n = 37, 69.8%). Compared to non-hesitant parents, VHPs significantly more often endorsed accident/injury, deterioration of the child's immune system, diet, environmental pollution, general stress, parents' negative views, parents' behaviors/decisions, parents' emotional state, and vaccines as causes for ASD. VHPs also had higher scores on the Personal Control, Treatment Control, Illness Coherence, and Emotional Representations subscales of the IPQ-R than did non-hesitant parents. In the final model, ASD-related vaccine hesitancy was significantly associated with higher scores on the Emotional Representations subscale (OR = 1.13, p = 0.10), agreement with deterioration of the child's immunity as a cause of ASD (OR = 12.47, p < 0.001), the child not having achieved fluent speech (OR = 2.67, p = 0.17), and the child experiencing a developmental plateau (OR = 3.89, p = 0.002). Findings suggest that a combination of child functioning and developmental history, as well as parents' negative views about and their sense of control over ASD, influence vaccine hesitancy among parents of children with ASD.

A qualitative study examining pediatric clinicians' perceptions of delayed vaccine schedules

OBJECTIVE

To explore pediatric clinicians' attitudes, beliefs, and perceived social norms about the impact of delayed vaccine schedules on the clinical management of their patients.

METHODS

We conducted 30 semi-structured qualitative interviews with academic (Infectious Diseases, Emergency Medicine) and community pediatric clinicians (General Pediatrics) to explore clinicians' perspectives on how delayed schedules influence their clinical management of patients. The interview guide was based on the Theory of Planned Behavior. We analyzed interview transcripts using both an inductive and deductive thematic approach.

RESULTS

The pediatric clinicians in our study overwhelmingly supported the recommended schedule, sought guidance on approaches to navigating conversations with vaccine hesitant families, and desired more evidence to effectively promote on-time vaccination. Clinicians described how delayed schedules have consequences for sick children (e.g., increased antibiotics, laboratory tests, emergency department visits) and healthy children (e.g., increased vaccine visits, out-of-pocket costs, fears among children receiving frequent shots). Clinicians stated that delayed schedules also negatively impact pediatric practices (e.g., increased time counseling patients, staff burden, clogged clinic space, unpredictable vaccine utilization, costs).

CONCLUSIONS

Pediatric clinicians perceive that delayed vaccine schedules negatively affect patients, pediatric practices, the healthcare system, and society. Future research should quantify the consequences of delayed schedules and identify strategies that promote vaccine adherence. Results from future studies can better support clinician-parent conversations about vaccine hesitancy, guide decision-makers about practice-level approaches to vaccine schedules, and advise payors and policymakers regarding vaccine-related policies.