Fever after the hepatitis A vaccine

Vaccination trains the immune system, and some people develop a mild fever, tiredness, or soreness near the injection site afterward. These effects generally settle as the immune response calms. A fever may also be unrelated and could reflect an infection that began around the same time. The vaccine cannot cause hepatitis A infection. Note when the temperature began, how it was measured, and whether other symptoms are present.

Encourage rest and regular fluids. Use light clothing and avoid overheating. A cool cloth can soothe the injection area; do not rub or press it repeatedly. Ask a pharmacist or clinician which fever medicine is suitable, particularly for a child, pregnancy, liver disease, or other medicines. Follow the product instructions and do not give aspirin to children. Keep the vaccination record available for any review.

Seek emergency help for trouble breathing, swelling of the face or throat, widespread hives, collapse, or marked drowsiness soon after vaccination. Contact a clinician for a fever that is high, worsening, prolonged, or accompanied by repeated vomiting, severe headache, dehydration, or a child who is difficult to comfort. A clinician can decide whether the timing fits a vaccine response or whether another cause needs examination.

Ask whether the temperature fits a vaccine reaction, which medicine and dose are appropriate, whether another vaccine dose should proceed, and which symptoms require immediate help.