A nurse is preparing to administer the influenza vaccine to a 65-year-old client. Which assessment finding would require the nurse to delay the vaccination?

The primary reason to defer an inactivated influenza vaccine (IIV) is a moderate or severe acute illness with or without fever. This precaution prevents superimposing vaccine side effects on the underlying illness or confusing the clinical picture. Vaccinate after the acute episode resolves.

A mild illness (e.g., afebrile upper respiratory infection) is not a reason to delay. A normal oral temperature like 98.8°F (37.1°C) confirms the absence of significant fever.

A shellfish allergy is not a contraindication or precaution. The only allergy requiring deferral is a severe allergic reaction (e.g., anaphylaxis) to a prior influenza vaccine dose or its component (e.g., egg protein).

Inactivated influenza vaccine can be given simultaneously with other inactivated vaccines (e.g., pneumococcal) or at any interval. No waiting period is needed.