## 3 Materials and Methods
### Chatbot Intervention Program Development  
In this study, we used the Kakao Plus Friend platform, which contains 94.4% of the Korean population [18], to deliver a chatbot intervention program to provide real-time child vaccination consultation. The chatbot developed for this study provides information on child vaccination with 1:1 customization, a feature enabled by building an algorithm appropriate for each child by considering their age without the need to expose the counseling content to others. During the first testing stage, the dialogue content of the prototype chatbot was constructed using Dialogflow, supported by Google. Dialogflow is a convenient program which can apply natural language learning to chatbot implementation and can be linked to Kakao i Open Builder [19]. Through the Dialogflow program, keywords for 17 infectious diseases and 17 types of vaccines suggested by the KCDC website were included. By entering the keywords can lead to finding nearby health centers, vaccination schedules, nationally designated vaccinations, other vaccinations, and information regarding vaccination medical institutions. Representations of the child vaccination chatbot based on Kakao Plus Friend are shown in Figures 1-4. If the candidates agreed to participate, they were registered, and a survey was sent to a 1:1 chat room. The structure of the chatbot is shown in Figure 5. The child vaccination chatbot service scenario is presented in Table 2.  
The conversation below shows the questions raised by parents to the chatbot. The conversation occurred in real time. Real-time Conversation 1. Parent: Hello:) Today, my two-year-old baby was vaccinated with the 3 rd round of Japanese encephalitis and meningococcus (Menbio). Chatbot: Yes, understood  
Parent: However, the doctor told me that the meningococcal vaccination requires another vaccination two months later. Which is confusing because I thought only one round was enough. Chatbot: So what is your main question? Parent: How many vaccinations do I need in total? I wonder if one-time vaccination is enough. Chatbot: There are two types of meningococcal vaccines available in Korea. First, Menveo: From 2 months to 55 years of age, 1 dose. If vaccination is started at 2-6 months, 3 doses at 2-month intervals 4 th vaccination is 6 months at intervals. Inoculation after 1 year of age 2 doses if the vaccination is started between 7 and 23 months of age  
Second, Menactra: 9-23 months 2 doses at 3-month intervals. 24 months-55 years of age 1 dose. The frequency of vaccination varies depending on when your child is vaccinated and the type of medication. * For details such as the inoculation period and frequency of inoculation, you need to consult with your assigned doctor. Parent: I am worried about the vaccination my child will receive today whether it requires two times of vaccination to generate antibodies. Chatbot: The age and frequency of vaccination may vary, so consult with a specialist before vaccination. Parent: Thank you  
Real-time Conversation 2. Parent: After child vaccination my child has a mild fever. What shall I do? Chatbot: Check the child's temperature regularly. Parent: The temperature is 37.3 degrees  
Chatbot: Apply a lukewarm temperature wet towel and gently massage the child's body avoiding the vaccination area. Parent: When should I see the pediatrician? Chatbot: If the temperature goes above 38 degrees and doesn't drop consider visiting the hospital. The reason for using the chatbot based on an SNS platform, Kakao Plus Friend, is because this is the most widely used domestic SNS platform in Korea. \"Kakao talk\" is a widely used messenger service similar to WhatsApp, WeChat, etc. Comparing methods of information provision by conventional documentation, websites, and chatbot information update speed can be performed in real time and provides information related to the context, while conventional documentation and websites do not. The chatbot can also provide a two-way interaction and customized information.