Introduction

In the United States (US), children as young as 5 years old became eligible for the Pfizer-BioNTech COVID-19 vaccine in October 2021 [1]. Studies of the vaccine in real world settings have found it to be highly effective in preventing severe disease and reducing hospitalization among children and adolescents [2,3]. However, despite wide availability of vaccines in the US, many children remain unvaccinated and vaccine uptake appears to have slowed [4]. On May 25, 2022, just 51% of children ages 5–17 had received at least one dose of a COVID-19 vaccine. By September 21, 2022, rates had risen by just one percentage point to 52% [5]. This is a lower rate compared to coverage levels of many other similarly recommended immunizations seen in the past. For instance, in the 2018–2019 school year, 63% of children between 6 months and 18 years received a flu vaccine [6]. Likewise, the coverage rate for the meningococcal conjugate (MenACWY), a disease with similarly rare but severe effects, was 89% among adolescents in 2020 [7].

According to the Centers for Disease Control and Prevention (CDC), as of September 2022, there have been over 15 million COVID-19 cases, over 12,200 laboratory-confirmed COVID-19 associated hospitalizations, and over 1,700 COVID-19 deaths among children in the United States (US) [8,9]. While adults have faced much higher acute morbidity and mortality, long term impacts of the disease on children are still unclear. Recent estimates from the United Kingdom suggest that around 5% of all secondary school students have experienced Post-COVID Conditions [10]. Additionally, children have faced far-reaching secondary effects from the pandemic, including disrupted healthcare services, routine immunizations, and education, and an increased prevalence of mental health disorders such as anxiety and depression [11].

Given the large disparities in vaccine coverage between COVID-19 and routine pediatric immunizations, increasing COVID-19 vaccination rates among children may require new strategies. Much prior work has been devoted to understanding COVID-19 compliance among parents. Prior studies have found vaccinated parents much more likely to vaccinate their children and that side effects and vaccine safety are two of the most common reasons for concern [4,12–22]. However, prior studies often analyzed all parents as a single cohort, rather than investigating this heterogeneity. Additionally, prior research has been limited by potentially non-representative samples. In this large, diverse, and nationally representative study, we aim to identify the demographic factors associated with parental compliance for COVID-19 vaccination among children in the United States and reasons for refusal. We also examine heterogeneity among vaccinated and unvaccinated parents through the inclusion of numerous relevant predictor variables and detailed information on reasons for refusal.

Methods

To understand compliance for child vaccination against COVID-19, we administered an online survey focusing on parents with children ages 5–17, and analyzed responses using survey weights, logistic regression, and cluster analysis.

Results

Of the 217,023 survey respondents, 3,301 were under the age of 18 and excluded. An additional 159,752 users were excluded for not having children 17 or under and 10,098 users were excluded for having children under the age of 5. Next, 9271 respondents were excluded for missing data on variables of interest. Lastly, 3,410 parents were removed who were always unsure about vaccinating their children, and 1,051 were removed for only intending to vaccinate some of their children, leaving a total sample of 30,140. After exclusion, the mean survey weight of participants was .98, leading to a weighted sample of 29,583 (S1 Fig).

Of the 29,583 surveyed parents, 7,654 (26%) were unvaccinated, 2,697 (9%) were partially vaccinated, 9,713 (33%) were fully vaccinated, and 9,519 (32%) were fully vaccinated and boosted. A total of 19,586 (66%) parents expressed willingness to vaccinate their child. Parent characteristics are listed in Table 1. About half of participants were female, and a majority were White, religious, employed, and insured. A plurality of parents were ages 40–49 years, and had a household income under $49,999. S3 Table displays summary characteristics of parents who were always unsure or held inconsistent preferences across their children.

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Table 1. Characteristics of studied participants.

https://doi.org/10.1371/journal.pdig.0000147.t001

We observed a high degree of concordance in preferences, with 86% of vaccinated parents willing to have their children vaccinated and 85% of unvaccinated parents unwilling to have their children vaccinated. We observe that 70% of partially vaccinated parents, 77% of fully vaccinated parents, and 95% of fully vaccinated and boosted parents are willing to have their children vaccinated (S4 Table). In a pooled regression of all parents, willingness to vaccinate children was independently associated with a number of factors (Table 2). Major predictors of parents’ preferences for child vaccination included being fully vaccinated and boosted (odds ratio [OR]: 106.0, 95% confidence interval [CI]: 93.9–120.0), Democrat political affiliation (OR: 4.22, CI: 3.82–4.66), and Asian race (OR: 3.07, CI: 2.56–3.71) (Fig 1). We find statistical differences between all parental vaccination status levels regardless of reference level chosen (S5 Table). VIF analysis suggested there exist limited cross-correlation among correlates (squared scaled GVIF threshold of 5). A sensitivity test across age, education, income, and political party finds the effect of parental vaccination status on willingness is consistent across parent level subgroups (S6, S7, S8 and S9 Tables). The model achieved an accuracy of 0.87 using a 50% cut off probability and an AUC of 0.91 when training on 80% of the sample and testing on the remaining 20%. In a model not using parent vaccination status as a determinant of willingness, we found that major predictors of parents’ preferences for child vaccination still include Democrat political affiliation (OR: 6.03, CI: 5.57–6.53) and Asian race (OR: 5.15, CI: 4.37–6.09). In addition, we found that high income and having health insurance were independently positively associated with willingness, whereas we observed negative associations in the model including parental vaccination status.

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Fig 1. Predicted probabilities of vaccinating child.

https://doi.org/10.1371/journal.pdig.0000147.g001

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Table 2. Multivariate relationship between parent characteristics and willingness to vaccinate children.

https://doi.org/10.1371/journal.pdig.0000147.t002

Several correlates of willingness differed in our separated regression models of unvaccinated and fully vaccinated parents (Table 2). Among fully vaccinated parents, willingness was independently positively associated with older age, college education, atheism/agnosticism, receiving an mRNA vaccine, and no vaccine side effect of headache, nausea/vomiting, or rash. Among unvaccinated parents, willingness was independently positively associated with male gender, younger age, high school or less education, and a lack of health insurance.

The 9,998 parents who were unwilling to vaccinate their children listed several reasons for refusal (S2 Table). Overall, parents were most concerned about potential side effects (47%) and the vaccine being too new (44%). Vaccinated and unvaccinated parents differed on several concerns. For example, unvaccinated parents were much more likely to list a lack of trust in government (41% to 21%, p < .001) and a lack of trust in scientists (34% to 19%, p < .001) as reasons for refusal. Parents with older children are more likely to say the decision to vaccinate should be the child’s decision when they are of appropriate age while parents with younger children are more likely to say their children are too young to be vaccinated (S10 Table).

Cluster analysis of unwilling parents’ reasons indicated that 3 clusters achieved a good balance of interpretability and cluster quality. These clusters differ significantly on both reasons for reluctance and parent characteristics (Table 3). For instance, Cluster 1 parents (32%) had a median of 8.0 reasons for refusal, were very likely to lack trust in government and scientists, were very likely to think the vaccine was too new and worry about potential side effects, and were likely to view the pandemic as already being over. Cluster 2 parents make up the majority of all unwilling parents (56%). Parents in this cluster had a median of 1.0 reasons for refusal and a majority (53%) had a high school or less education. Cluster 3 parents were the smallest group, had a median of 4.0 reasons for refusal, and were very likely to think the vaccine was too new and worry about potential side effects.

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Table 3. Summary characteristics by clusters of unwilling parent.

https://doi.org/10.1371/journal.pdig.0000147.t003

In addition, 73% of parents in Cluster 1 are unvaccinated, while 61% and 59% of parents in Clusters 2 and 3 are unvaccinated, respectively. However, we find that the three types of vaccinated parents (partially vaccinated, fully vaccinated, fully vaccinated and boosted) are relatively evenly distributed across the three clusters.

Discussion

In this study, we aimed to identify the determinants of parental COVID-19 vaccine compliance and the main motivating beliefs for reluctance to vaccinate children among unwilling parents. We found parental vaccination status to be a large predictor of parent preference for child vaccination. In addition, we find heterogeneity among parents both in correlates of willingness and reasons for reluctance. For instance, several correlates differed by parental vaccination status. Among the unvaccinated, younger age and lower education were associated with willingness, and among the vaccinated an inverse association was observed. Reasons for refusal to vaccinate children also differed by parental vaccination status with unvaccinated parents less likely to trust government and scientists. Unwilling parents can be divided into three categories based on their reasons for reluctance. To our knowledge, this is the first study to use a cluster analysis on parental vaccine refusal. Additionally, previous research has suggested that the survey is representative of the larger population in weighted demographic categories [25].

Our findings on the correlates of willingness to vaccinate children against COVID-19 are generally consistent with previous studies. Previous research has found vaccinated parents much more likely than unvaccinated parents to be willing to vaccinate their children [8,12–22]. Prior studies have also found likelihood of child vaccination higher among parents of older children, older parents, higher educated parents, Democrat-affiliated parents, insured parents, higher income parents, Hispanic and Asian parents, parents with routine influenza vaccine behavior, and male gender [12,13,15,21,22,31,32]. Unlike past research, we find lower income parents have higher odds for willingness on three of four multivariate models. We additionally find an inverse relationship between willingness and higher age and education among unvaccinated parents.

Prior research on barriers to COVID-19 vaccination parental compliance have found top reasons are often trust related, including vaccine safety and effectiveness, side effects, and lack of trust in government [12–15]. We find consistent results with past studies in the prevalence of concerns over vaccine safety, side effects, and lack of trust in government. However, we find that for a majority of parents (Cluster 2), side effects rarely factor into the decision to vaccinate children, suggesting non-trust related considerations such as accessibility or apathy as the main factors driving hesitancy among this group. Simply looking at the top concerns across parents then, will ignore important distinctions. Moreover, parents in Cluster 1 and Cluster 3 both have severe trust concerns, with large portions in both groups concerned about side effects and the speed at which the vaccine was developed. Yet a large majority of Cluster 1 parents exhibit a lack of trust in government or scientists while a small minority of Cluster 3 parents exhibit a lack of trust in both. Treating parents with side effect concerns as a homogenous group may ignore important differences and may fail to sufficiently ease their concerns.

Several limitations must be considered in interpreting the study results. First, bias is expected from any observational study conducted using a convenience sample; those willing to participate in our study may not be representative of the public as a whole and our findings may not be generalizable to the broader US population. The use of survey weights and the anonymity of the survey may help lessen this bias and prior work suggests the survey is well-targeted at representing the demographics of the US [25]. However, some non-targeted groups are likely underrepresented such as those lacking internet access. Second, we did not have direct measures of certain variables of interest such as child COVID-19 vaccination status and instead must rely on self-report. However, previous research on this survey’s estimates have shown it to track closely with CDC estimates for overall vaccination rates as well as alternative estimates for pandemic behavior such as mask wearing across the US [24,33]. Third, results may be limited by the dynamic nature of the COVID-19 pandemic with changes in public policy, public health recommendations, and case prevalence during the study period. For instance, parents today may express different preferences towards vaccinations as newer options become more available such as Novavax and new variants circulate. Fourth, this analysis solely focuses on understanding vaccine preferences at the individual-scale and ignores the dynamics of community- and region-level factors. Prior research highlights the importance of studying these dynamics at the community level with spatial clustering potentially leading to outbreaks even when aggregate vaccination coverage is high [34].

Willingness to vaccinate children is associated with many different parental characteristics with parent vaccination status being a major determinant. The results presented here can inform the further work needed to tailor child vaccination efforts to subgroups of parents who are more reluctant. It is important to acknowledge that predictors of parental vaccine willingness differ among vaccinated and unvaccinated parents and that examining unwilling parents’ concerns in aggregate will obscure many important distinctions.

Supporting information

Acknowledgments

The authors thank Kara Sewalk and the SurveyMonkey research team (Laura Wronski, Tim Gravelle & Jon Cohen) for their assistance. Mr. Sehgal had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.