## 1 Introduction  
Vaccination is considered the safest and most effective way to protect children from contagious diseases. According to the Korean National Health Data report \"2018 Children's Regular Vaccination Rate\", released in 2019, 96.8% of Korean children over 12 months old were vaccinated. However, there was a decrease in vaccination rates as children grew older, with rates of 94.7% for children aged 24 months and 88.3% for children aged 72 months [1]. Various factors affect the reduction in vaccination rates, including several sociodemographic [2] and parental factors. Parents' health beliefs have a direct impact on their children's vaccination status, as children are unable to direct their own health behavior. Furthermore, the American Centers for Disease Control (CDC) reported that the ongoing COVID-19 pandemic has contributed to a decrease in overall child vaccination rates [3]. Parents concerned about exposing their children to COVID-19 might contribute to the observed decline [3]. Additionally, according to national data from the Korea Disease Control and Prevention Agency, between the first quarters of 2019 and 2020, there was a decrease in pediatric vaccine administration, likely influenced by COVID-19 [4]. To prevent such declines, it is essential to provide timely vaccination-related information to parents, reminding them of the vital need to protect their children against serious vaccine-preventable diseases, even as the COVID-19 pandemic continues. Previous research emphasizes the importance of providing adequate information regarding child vaccinations. According to [PERSON] et al. (2018)'s research, providing parents with child vaccination information can improve parental awareness of vaccinations, which can raise vaccination rates. Moreover, it showed that providing educational intervention for parents or child immunization-related information can have a positive influence on vaccination rates. As shown in the previous research, one of the important factors in vaccination implementation is the provision of vaccination information to parents. In Korea, vaccination-related information is provided to parents by health centers, hospitals, and clinics. Additionally, parents use analog child vaccination notebooks to record their children's vaccination information. The weakness of traditional methods includes mistaken records and loss of vaccination notebooks, which may lead to missed vaccinations [5]. Improvements to existing vaccination management practices are needed. A chatbot could supplement existing methods, as it can provide vaccination-related information in real time. According to [PERSON] et al. (2019), people tend to use a chatbot for minor health problems. Public health organizations and pediatric clinics provide repeated trivial vaccination-related information. The Q&A (question and answer) method of chatbots is similar to FAQs. However, it is different in the speed of providing answers because it usually provides information in real time with appropriate answers ([PERSON], [PERSON], and [PERSON], 2015). Considering these points, using mutual communication techniques to encourage child vaccination has a positive effect on vaccination decision making [6; 7; 8]. However, the importance of vaccination management for children is easily neglected and research on vaccination has been limited to studies mainly on vaccination awareness and satisfaction, as well as on vaccination status and related factors [9; 10; 11; 12; 13]. Few studies have been conducted on chatbots in this context. Awareness and dissemination of information could potentially improve if parents used technical tools, such as chatbots, when raising their children [14]. Therefore, receiving vaccination information through a chatbot channel is expected to contribute to boosting vaccination rates because relevant information can be provided more effectively than when using traditional methods. The purpose of this study is to develop a real-time consultation messenger service chatbot for vaccination questions and answers.