Knowledge, Attitudes, and Practices Regarding the COVID-19 Vaccine for Children: A Questionnaire Survey at the 18-Month Health Check-Up

1. Introduction

As of July 2024, SARS-CoV-2 had infected more than seven hundred million people worldwide, including children, and had killed almost seven million people since the start of the COVID -19 pandemic [1]. Although children are known to have lower morbidity and mortality rates from COVID-19 compared with adults, immunocompromised individuals and children with some underlying conditions can experience severe symptoms [2,3], and even healthy children sometimes develop life-threatening conditions such as myocarditis and multisystem inflammatory syndrome [4,5,6].

Vaccines are an effective tool for reducing the incidence and mortality rates of COVID-19. Since 2020, more than 13 billion COVID-19 vaccine doses have been administered globally, and 73% of the world’s population has received at least one dose as of July 2024 [7]. The efficacy and safety of the vaccine are well-established in children; past studies have confirmed that administration of the COVID-19 vaccine to children aged 6 months to 5 years is safe and generates a sufficient immune response [8]. Furthermore, large-scale cohort studies have shown that COVID-19 vaccination is effective against infections of the Omicron variant and severe outcomes in children aged 0–11 years [9].

Despite these evidences, the vaccination rate among children has been low in some countries [10,11]. Previous studies found that child vaccination coverage and confidence increased with parental age [12,13,14]. Other factors, including parental vaccination status, previous influenza vaccination, educational attainment, annual household income, race/ethnicity, prior COVID-19 diagnosis, the vaccine approval process, and trust in the child’s doctor as well as social media, are also associated with the likelihood of children being vaccinated against COVID-19 [10,15]. Vaccine hesitancy might persist during a future pandemic; therefore, it is necessary to analyze the factors that led to the underutilization of COVID-19 vaccines in children to develop better strategies for vaccine uptake.

In Japan, the BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine was approved by the Ministry of Health, Labor and Welfare of Japan in February 2022 for children aged 5–11 years, and in October 2022 for children aged 6 months to 4 years. However, the Japanese government has not indicated a policy to promote COVID-19 vaccination for children, leaving the decision to vaccinate up to individual pediatricians and parents. As a result, the vaccination rate in Japan remains low. As of April 2024, only 4.5% of children aged 6 months to 4 years had received at least one dose, compared with 80.4% across all age groups [16]. A previous study has clarified that parental COVID-19 vaccine reluctance is strongest among parents with infants [17]. Thus, we aim to address the knowledge, attitudes, and practices (KAP) of this population in terms of parental COVID-19 vaccine acceptance and hesitancy.

2. Materials and Methods

2.1. Study Design, Setting and Population

This cross-sectional study was conducted from February to May 2024 in the city of Toyonaka, Osaka Prefecture. Having the second lowest COVID-19 vaccination rate among prefectures in Japan, Osaka Prefecture was considered a suitable target for investigating the reasons underlying the lack of success in vaccine promotion [17], while Toyonaka was chosen because it is a core city (a classification of Japanese cities based on certain criteria such as population size and economic importance). The population of Toyonaka is approximately 398,000 people, including 72,000 children. The average household income in Toyonaka is higher than the average household income in Japan, indicating a high economic level.

2.2. Sample Size

The effective sample size for a single population was estimated using Raosoft software (http://www.raosoft.com/samplesize.html accessed in October 2023). In Toyonaka, the annual number of births is 3,000 and the sample size was calculated considering a 95% confidence interval (CI), a 5% margin of error, and a 50% response distribution. Assuming a non-response rate of 10%, the final sample size was estimated as 375.

2.3. Sampling Methods

In Japan, health check-ups are mandatory for infants at 18 and 36 months of age. These check-ups include physical measurements, assessments of growth and development, and confirmation of vaccinations. We conducted a paper-based, household survey on the 18-month health check-up at Toyonaka Health Center. Questionnaires were distributed in coordination with the health center in advance to all households with 18-month-old infants, and the responses were collected on the day of the health check-up. We made efforts to minimize sampling errors by determining an adequate sample size and maintaining consistency in our survey methods and question content, ensuring that the data obtained accurately reflected the entire population.

2.4. Questionnaire

All answers were multiple-choice, with an option for a free-form response if necessary. The questionnaire covered four domains. The detailed question content is provided in the Supplementary Material.

Domain 1: COVID-19 vaccination status in children aged 17–20 months

Vaccination status was reported by the child’s parents or guardians. Answering “Yes” to the question of whether your child has received a COVID-19 vaccine was considered to indicate a vaccination history. The respondent also provided information on the number of doses their child had received and the child’s age in months when the initial vaccination was administered.

Domain 2: Knowledge and attitudes regarding the COVID-19 vaccine in households with a vaccinated child aged 17–20 months

Households in which the child had received a COVID-19 vaccine were asked two questions. The first assessed the main reason for vaccination, while the second assessed the factors in the respondent’s decision to vaccinate their child. The respondents selected the response that most applied to each question.

Domain 3: Knowledge and attitude regarding the COVID-19 vaccine in households with a non-vaccinated child aged 17–20 months

Households in which the child had not received a COVID-19 vaccine were asked two questions. The first assessed the main reason for non-vaccination, while the second assessed the factors in the respondent’s decision not to vaccinate their child. The respondents selected the response that most applied to each question.

Domain 4: Intention to vaccinate against COVID-19 among households with a non-vaccinated child aged 17–20 months

Respondents with a child who had not received a COVID-19 vaccine were asked if they planned to have their child vaccinated in the future.

2.5. Analysis

Data entry and analysis were performed using R ver. 4.2.2. Using the answers from Domain 1, factors influencing the respondents’ decisions to vaccinate their children were assessed. Univariate and multivariate analyses were performed using logistic regression to calculate crude odds ratios (ORs), adjusted ORs, p-values, and CIs. The dependent variable was the child’s COVID-19 vaccination status, and explanatory variables were chosen based on their clinical relevance and included the following: Respondent’s age, respondent’s employment status, whether the respondent is a healthcare professional, respondent’s vaccination status, whether the respondent has received the COVID-19 vaccine three or more times, family member’s COVID-19 infection status, whether a family member experienced moderate to severe COVID-19, including death, whether the child was a premature baby, whether the child has any underlying medical conditions, whether the child has received routine vaccinations, and child’s COVID-19 infection status

The effective sample size for a single population was estimated using Raosoft software (http://www.raosoft.com/samplesize.html accessed in October 2023). In Toyonaka, the annual number of births is 3,000 and the sample size was calculated considering a 95%CI, a 5% margin of error, and a 50% response distribution. Assuming a non-response rate of 10%, the final sample size was estimated as 375.

2.6. Ethics Approval

This study was approved by the Committee for Ethical Review of Observational studies, National University Corporation, University of Osaka Hospital, School of Medicine (December 11, 2023). The study was conducted in accordance with the principles of the Declaration of Helsinki. A confirmation section regarding consent for the survey was provided at the beginning of the survey sheet, and respondents were asked to check if they agreed. The respondents were informed of the methods, use of data, purpose, and significance of the study, its anonymous, confidential nature, and their ability to withdraw consent at any time.

3. Results

3.1. Response

Response sheets were mailed to 1,060 households, and 960 children attended the 18-month health check-up. A total of 671 survey sheets were sampled and 665 respondents agreed to participate in the study. Among the respondents, 96% were women, and 11% were healthcare providers. The median age of the respondents was 34 years, and 28% were unemployed. In terms of the COVID-19 vaccination status, 16.4% of the respondents had no history of COVID-19 vaccination, while 53.4% had received three or more doses of the COVID-19 vaccine. The median age of the children was 19 months; 2.7% were born prematurely, and 3.6% had underlying medical conditions. Almost all (99%) of the children had received the standard immunizations (Table 1).

3.2. Domain 1: COVID-19 Vaccine Status in Children

Only 25 (3.8%) of the children had a history of COVID-19 vaccination, with a median of three doses, and the median age at vaccination was 7 months (Table 1). In the statical analysis, most of the planned variables could not be assessed because no respondents who had vaccinated their children selected either answer. Only five variables could be analyzed: the respondent’s age, whether the respondent is a healthcare provider, whether the respondent had received three or more doses of the COVID-19 vaccine, family member’s COVID-19 infection status, and child’s COVID-19 infection status. The univariate analysis revealed that whether the respondent had received three or more doses of COVID-19 vaccine and family member’s COVID-19 infection status were associated with the child’s COVID-19 vaccination status. However, in the multivariate analysis, only whether the respondent had received three or more doses of the COVID-19 vaccine was associated with the child’s vaccination status (adjusted OR 8.24, p < 0.01) (Table 2).

3.3. Domain 2: Knowledge and Attitudes Regarding the COVID-19 Vaccine in Households with a Vaccinated Child Aged 17–20 Months

Among the 25 respondents who had their child vaccinated, 7 (28.0%) answered that their reason was the belief that vaccines can prevent long-term effects and complications. The same proportion also responded that COVID-19 is a serious infection that can lead to severe illness or death, even in infants and young children without underlying health conditions (Table 3). Regarding the sources that had influenced their decision to vaccinate, 4 (16.0%) indicated that their main source of information was social media platforms such as Facebook, Instagram, and Twitter (now X), where medical doctors and celebrities share information. Following this, television and online news, advice from their family, and advice from a primary care physician each accounted for 12% (Table 3).

3.4. Domain 3: Knowledge and Attitudes Regarding the COVID-19 Vaccine in Households with a Non-Vaccinated Child Aged 17–20 Months Old

Among the respondents who did not vaccinate their child, 38.9% indicated that their decision was due to insufficient data on the safety of the vaccine, followed by 17.2% of respondents who expressed concerns about potential side effects (Table 4). Approximately 26.7% of respondents reported that the primary source of information influencing their decision was television and online news, followed by 16.7% who indicated that the main factor was advice from their family (Table 4).

3.5. Domain 4: Intention to Vaccinate Against COVID-19 Among Households with a Non-Vaccinated Child Aged 17–20 Months Old

Of the 640 respondents with children who had not received any COVID-19 vaccines, 1.2% answered that they were planning to get the COVID-19 vaccine in the future, 32.0% answered that they were definitely not getting the COVID-19 vaccine in the future, and 64.7% answered that they would wait a while to see how the COVID-19 infection situation progressed or that they were not sure (Table 5).

4. Discussion

This KAP survey revealed a low rate of vaccination against COVID-19 among children aged 17–20 months in Toyonaka, Osaka. Indeed, only 3.8% of children were found to have received at least one dose of the COVID-19 vaccine. This finding is in line with past surveys [14,15]. During the COVID-19 pandemic, although occasional cases with severe complications or deaths were reported, low vaccination rates did not lead to any serious consequences because of the low severity of COVID-19 in children [18]. However, it is important to elucidate the reasons underlying the low vaccination rates because there is no guarantee that children will have mild cases in a future pandemic.

The present survey revealed that parents receiving three or more doses of the COVID-19 vaccine was the most important factor associated with the likelihood of the child receiving one or more dose of the vaccine. This finding is in line with a previous study in which parents who received one or two doses of the COVID-19 vaccine were significantly more hesitant to vaccinate their children compared with those who received more than two doses [19]. At the end of April 2021, 2.0% of the Japanese population had received at least one dose of COVID-19 vaccination and at the end of October of the same year, the vaccination rate had risen rapidly to 80.0%. During this period, the momentum in society towards COVID-19 vaccination had grown as a result of various interventions: the mobilization of the Japanese Self Defense Forces, the establishment of mass vaccination slots targeted only at the younger population from teens to those in their thirties, and COVID-19 vaccination for athletes, coaches, and other individuals participating in the Tokyo Olympics. Given that the second dose of the COVID-19 vaccine was already being administered during this period, it is possible that more people were influenced by societal momentum to get vaccinated. Against this background, the decision on whether to receive a third dose may have been influenced less by societal momentum and more by each individual’s knowledge-based reasoning and action because the third dose of the COVID-19 vaccine started in Japan after the peak of the social momentum. It can be speculated that children are more unlikely to be vaccinated compared with other groups. Notably, this survey found that among children with underlying medical conditions, none had received the COVID-19 vaccine. These results highlight the fact that vaccines do not reach the children who truly need them.

This survey also reflects the respondents’ knowledges and attitudes toward vaccinating their children. The majority (56.1%) of reasons for not vaccinating children against COVID-19 were related to concerns about safety and side effects. This confirms the findings of past studies [15,19,20,21,22]. One-fourth (26.7%) of the respondents cited television or online news as the main factor that influenced their decision not to vaccinate their children. This result contradicts past research findings on the relationship between COVID-19 vaccine uptake and information sources among adults. A previous study showed that individuals who relied on traditional news sources, including television, radio, news websites, or newspapers, were more likely to vaccinate their children compared with those who relied on other sources such as social media platforms [23]. Previous studies have reported that social media platforms have a negative impact on COVID-19 vaccination behavior [24]. However, in the present survey, only 9.3% cited social media platforms as a factor in their decision not to get the COVID-19 vaccine. Television and online news can disseminate information about COVID-19 vaccines to a large population at once. Thus, a method for swiftly assessing misinformation or inaccuracies using public–private partnerships is urgently needed.

Other trusted sources of information influencing the decision to vaccinate their children were television or online news, advice from their family, and advice from their primary care physician (12.0% each). As previous studies have revealed, recommendations and effective communication by primary care clinicians have a large impact on the decision to vaccinate [25,26]. Thus, pediatric providers need to communicate effectively to make vaccinations more accessible and must work to eliminate vaccine hesitancy in order to prepare for a future pandemic.

In Japan, vaccination coupons were automatically issued to adult citizens, but the decision issue them to children depended on the local government. Toyonaka did not automatically issue these coupons to children, instead requiring parents to contact the health office to obtain them [16]. Although only 2 respondents (0.3%) cited the difficulty of obtaining a coupon as a reason for not vaccinating their children, the government’s passive approach may have deprived parents of the opportunity to consider vaccinating their children. The COVID-19 vaccination rate in Toyonaka was lower than the national average for infants (at least one dose: 4.5%), suggesting that there is room for improvement in making vaccines more accessible for children.

The findings of this study will contribute to the formulation of future public health practices. For households who received less than three doses of the COVID-19 vaccine, evidence-based communication between parents and primary care clinicians is needed. In addition, public–private partnerships should work to swiftly assess misinformation or inaccuracies. Furthermore, households with children having underlying medical conditions need to receive early guidance on various health risks associated with these conditions.

5. Conclusions

This KAP survey focused on the COVID-19 vaccine status of children under the age of 2 years. This survey confirms a low rate of vaccination against COVID-19 in Toyonaka, Osaka, especially among children with parents who received fewer than three doses of the COVID-19 vaccine. It also found that concerns about side effects and safety were significant factors underlying hesitation toward getting children vaccinated. Identifying the groups to be targeted with intervention as well as the attitudes among such groups suggest additional potential public health measures. The findings of this study may serve as a valuable contribution to preparedness for a future pandemic in an era where diseases can easily cross borders.