Final answer:
The best way for a medical assistant to assist a child during a checkup and immunization is by letting them hold a stethoscope to understand and be engaged in the process, while also informing the mother about vaccine safety.
Step-by-step explanation:
To assist the child and improve communication during a checkup and immunization, the medical assistant should let the child hold the stethoscope and listen to his own heart to understand what you will be doing. This approach not only distracts the child but also educates them about the process and can help reduce fear through understanding and engagement. Also, providing factual information on the safety and efficacy of immunizations can help alleviate concerns. For example, the mother can be informed that the study linking MMR vaccine to autism has been discredited and that vaccines are essential in preventing serious diseases such as measles, which has seen outbreaks due to a decline in vaccination rates.