Fever from shots: what should you know?

Vaccination trains the immune system, and the resulting response may cause warmth, tiredness, chills, or soreness near the injection site. Fever can begin after the appointment and often settles as the response eases. The timing alone cannot prove that every symptom came from the shot; an infection may start around the same time. Check the temperature with a reliable thermometer and consider the person's age, usual health, and other symptoms.

Offer frequent fluids or breastfeeds, allow rest, and use light clothing in a comfortable room. Do not use ice baths or alcohol rubs. If the person is uncomfortable, ask a pharmacist or clinician which fever medicine is suitable for their age and weight, and follow the label or prescribed instructions. Keep a note of the temperature, time of the shot, medicines given, and changes in behaviour. Avoid giving aspirin to children unless a clinician specifically directs it.

Get urgent help for trouble breathing, swelling of the face or throat, widespread hives, fainting, a seizure, marked drowsiness, confusion, a stiff neck, or a child who is difficult to wake. Seek prompt medical advice for a very young infant with a fever, repeated vomiting, signs of dehydration such as very little urine or a dry mouth, or a fever that is worsening, persistent, or accompanied by a new concerning symptom. A clinician can assess whether another illness, such as Common Cold, COVID-19, or Croup, is also possible.

Ask which reactions are expected after this particular shot, how to measure the temperature, which medicine and dose fit the person's age and weight, and what timing or symptoms should prompt a review.