Final answer:
To reduce fear in a 5-year-old child being admitted to the hospital, a nurse should prepare the child for the experience by using child-friendly explanations and resources to make the unfamiliar, familiar.
Step-by-step explanation:
The most effective intervention that a nurse can undertake to reduce negative feelings and fear in a 5-year-old child being admitted to the hospital is preparing the child for the hospital experience. This preparation can include explaining the procedures and environment in a child-friendly way, using toys and books to illustrate what will happen, and ensuring that the child understands that their caregiver will be close by. Preparing a child in advance can help them feel more in control and less anxious about the unfamiliar surroundings and people they will encounter in the hospital setting.