What should you know about fever from immunization?

Vaccination trains the immune system, and temporary warmth, soreness, tiredness, or fever may follow. The timing and vaccine type matter, and fever after an injection does not prove that the vaccine caused every symptom. An unrelated infection can begin around the same time. Note when the fever started, the vaccine received, the temperature, and whether there is a cough, rash, vomiting, breathing problem, or unusual sleepiness.

Offer fluids, allow rest, keep clothing light, and check the person regularly. For a child, continue breast or formula feeds as usual if tolerated. A fever medicine may be appropriate for discomfort, but use the product and dose advised for that person; never give aspirin to a child unless a clinician specifically says to. Do not rub the injection site vigorously or give extra doses simply to prevent a fever.

Get urgent help for breathing difficulty, facial swelling, widespread hives, collapse, a seizure, severe drowsiness, dehydration, or a child who is difficult to wake. Contact a clinician if fever is worsening, does not settle, returns after improvement, or comes with a concerning rash or repeated vomiting. A clinician can distinguish an expected reaction from an illness such as COVID-19, bronchiolitis, or another infection.

Ask which reactions are expected for the vaccine given, how to measure temperature, what medicine and dose fit the person, and when the next dose or review is due.