If an infant has just received the DTaP immunization, which symptom should prompt the parents to seek immediate medical attention?

Following the DTaP immunization, certain symptoms can indicate a more severe reaction that requires immediate medical attention. An inconsolable cry lasting more than three hours is considered a concerning sign.

This may be indicative of a reaction called excessive crying, which can sometimes be associated with an underlying issue such as encephalopathy or a more severe adverse reaction to the vaccine. The characterization of the crying as "inconsolable” suggests that typical comforting measures have failed, which warrants further evaluation to rule out any serious conditions.

In contrast, while a fever over 101°F or a rash at the injection site can occur post-vaccination, they are generally not urgent concerns unless accompanied by other alarming symptoms. A fever can be a normal immune response to the vaccine, and localized reactions such as a rash may resolve on their own. Frequent feeding or decreased appetite may also be common after vaccinations as infants can experience a temporary change in behavior, but this does not typically raise immediate concern unless more severe symptoms are present.