What is COVID-19 vaccination done with?

An mRNA vaccine carries temporary instructions that help cells make a harmless piece of the virus. The immune system responds to that piece and develops recognition, so it can respond more effectively if it encounters the virus later. The mRNA does not alter a person's genes, and the instructions are broken down after they have been used.

The injection is usually given in the upper arm. A sore arm, tiredness, headache, muscle aches or a mild fever can occur as the immune response develops. These effects generally settle without treatment, but a clinician can explain what to expect for your circumstances.

Tell the vaccinator about previous vaccine reactions, severe allergies, current illness, pregnancy, and medicines that affect immunity or bleeding. Follow the appointment advice about timing and observation afterwards. Stay for the recommended observation period so staff can respond promptly if an immediate reaction occurs.

For a clearer explanation of the technology, read about the [mRNA Vaccine](/materials/mrna-vaccine/). Keep your vaccination record and ask which dose or booster is appropriate for your age and health history.

Seek urgent medical help for trouble breathing, swelling of the face or throat, widespread hives, fainting, or severe weakness after vaccination. Chest pain, shortness of breath, or a racing or irregular heartbeat also needs prompt assessment. Contact a clinician if symptoms are worsening, prolonged, or difficult to distinguish from another illness.

Ask which vaccine is suitable for you, whether an earlier reaction changes your options, how to plan vaccination around another appointment, and which symptoms should prompt a same-day call.