Infant fever after vaccines: what parents should know

Vaccination introduces a harmless immune stimulus that teaches the body to recognise a target. As that response develops, some infants become warm, unsettled, sleepy, or feed less for a while. Soreness or redness where the injection was given can accompany the fever. These effects can begin after the appointment and generally settle without special treatment.

A fever is not automatically caused by the vaccine. An infection can begin around the same time, so consider cough, runny nose, vomiting, diarrhoea, a rash, or breathing changes. Fever can occur with conditions such as a common cold, bronchiolitis, croup, or cellulitis, but the symptom does not tell you which condition is present.

Take the temperature with a suitable thermometer, offer breast milk or formula often, and dress your baby lightly. Let them rest, check their breathing and responsiveness, and observe wet nappies. Keep the vaccination record available and note when the fever started, the readings, feeds, and any medicine given.

Use fever medicine only when advised for your infant’s age and weight, following the label or clinician’s instructions. Do not alternate products unless a clinician tells you to, and never use cold baths or ice to cool a baby. Contact the vaccination provider if you are unsure whether a reaction is expected.

Get emergency help if your infant has trouble breathing, swelling of the face or throat, widespread hives, a seizure, blue or grey skin, collapse, or is difficult to wake. Seek urgent advice for a very young infant with fever, repeated vomiting, poor feeding, markedly fewer wet nappies, a rapidly worsening injection site, or a baby who appears more ill rather than gradually improving. A fever with a new cough or noisy breathing also deserves prompt assessment.

Ask which temperature method to use, how long a post-vaccine fever may be watched, what dose of medicine is suitable, and whether the next vaccine visit needs any adjustment. Tell the clinician about previous reactions, current medicines, reduced feeds, and every symptom that appeared after the appointment.