What should you know about the Johnson & Johnson vaccine?

A viral-vector vaccine uses a harmless carrier to deliver instructions that train the immune system to recognise a target from the virus. The carrier does not cause the infection it is designed to prevent. This approach differs from an [mRNA Vaccine](/materials/mrna-vaccine/), which delivers messenger RNA instructions.

After vaccination, short-lived soreness, fatigue, headache, muscle aches, chills, or fever can occur as the immune system responds. Reactions vary, and the absence of symptoms does not show whether protection has developed.

Tell the vaccinator about allergies, previous vaccine reactions, pregnancy or plans for pregnancy, immune problems, recent illness, and medicines. Bring your vaccination history if available and follow the local schedule and product advice provided at the appointment.

Rest, drink fluids, and use symptom relief only as advised for you. Do not treat a previous mild reaction as proof that every vaccine is unsuitable; a clinician can review what happened and recommend a safe plan.

Contact a clinician for symptoms that are severe, persistent, or concerning after vaccination. Seek emergency help for trouble breathing, swelling of the face or throat, widespread hives, chest pain, fainting, or sudden neurological symptoms.

Is this vaccine appropriate for my medical history? Which product and schedule are recommended where I live? What reaction should I expect, and which symptoms should prompt urgent care?