Final answer:
The RN should examine the child's medical history for allergies, immune system health, illness, fever, and prior chickenpox or shingles infections before administering the varicella virus vaccine.
Step-by-step explanation:
Before administering the varicella virus vaccine to a 9-year-old child, the registered nurse (RN) should check the child's health history for several key factors. These include any previous history of severe allergies, especially to vaccine components, a weakened immune system, being pregnant or becoming pregnant soon for female patients, any recent blood transfusions or received other blood products, current illness or fever, and any history of chickenpox or shingles infections. If the child has had a previous severe allergic reaction to the varicella vaccine or any component of the vaccine, or if they are currently moderately or severely ill, the vaccination may need to be postponed. Additionally, it's important to determine whether the child has a condition that leads to a weakened immune system or if they are on therapy that affects the immune system, as this might indicate a need for caution or delay in vaccination. The RN should also advise the parents on what reactions might occur post-vaccination and when to seek medical attention.