A nurse is monitoring a 6-month-old infant 20 min after administering a hepatitis B immunization. Which of the following findings is the nurse's priority?

A. Prolonged crying: Prolonged crying can occur after an immunization, especially in infants, but it is generally not an immediate cause for concern unless accompanied by other symptoms such as difficulty breathing or skin changes. B. Temperature 37.7° C (99.9° F): A mild fever is a common side effect after immunizations and is usually not a cause for immediate concern. A temperature of 37.7°C (99.9°F) is within a normal range and typically resolves on its own. C. Hives on the child's neck: Hives (urticaria) can indicate an allergic reaction, which could potentially be a serious response to the immunization. An allergic reaction requires immediate attention and intervention, as it may progress to more severe symptoms such as difficulty breathing or anaphylaxis. D. Redness at the injection site: Redness at the injection site is a common and expected reaction following an immunization. It is generally not a cause for concern unless it is accompanied by severe swelling, pain, or other signs of infection.