Fever and vaccination: what to know

Vaccines train the immune system, and that activity can cause warmth, tiredness, soreness, or a raised temperature for a short time. The timing, vaccine type, age, health conditions, and other symptoms help a clinician judge whether the fever fits a common reaction.

A fever that starts later, keeps rising, or comes with cough, rash, diarrhoea, or breathing symptoms may have another cause. Illnesses such as common cold, chickenpox, COVID-19, or croup can occur around the same time as vaccination and are not automatically caused by it.

Check the temperature with a reliable thermometer and note when the fever began. Offer regular fluids, dress the person lightly, and allow rest. Use a fever medicine only when suitable for the person and exactly as directed on its label or by a healthcare professional; never give a child aspirin. Keep the vaccination record and product name available when asking for advice.

Seek urgent help for difficulty breathing, swelling of the face or throat, widespread hives, collapse, a seizure, unusual sleepiness, or a child who cannot drink. Contact a clinician promptly for a fever that is worsening, persistent, or accompanied by a concerning rash, severe pain, repeated vomiting, or signs of dehydration. Follow the vaccine provider’s specific after-care advice.

Ask how long a reaction is expected to last, which fever medicine is appropriate, whether the next dose should proceed, and which symptoms would change the plan.