Examples of mRNA vaccines: what to know

Messenger RNA, or mRNA, carries temporary instructions to cells. After vaccination, cells use those instructions to make a harmless piece of a virus protein. The immune system notices the protein, makes a response, and develops memory that can help it respond if it encounters the virus later. The mRNA is then broken down by the body; it does not alter a person’s DNA.

The vaccine does not contain a live virus capable of causing the infection it is designed to prevent. Vaccine products and recommendations can differ by age, pregnancy, health conditions, and local public-health guidance.

Tell the vaccinator about previous serious allergic reactions, current illness, pregnancy, immune-suppressing treatment, and any vaccines received recently. Follow the product instructions for observation after the injection. Soreness at the injection site, tiredness, headache, chills, or a mild fever can occur and often settle with rest and fluids. Use medicines for discomfort only as advised for you.

Seek urgent medical help for trouble breathing, swelling of the face or throat, widespread hives, fainting, chest pain, or a fast or irregular heartbeat after vaccination. Contact a clinician if symptoms are severe, worsening, or do not settle, or if you are unsure whether a new symptom is related to the vaccine.

Ask which mRNA vaccine is suitable for you, whether you need a dose now, how your medical conditions or medicines affect timing, and which symptoms should prompt urgent assessment.