What an attenuated vaccine means

The weakened organism can reproduce only to a limited extent, creating an immune response that resembles the response to natural infection. It is different from an inactivated vaccine, which contains killed organisms or selected parts of them. The MMR vaccine is a familiar live attenuated vaccine used to protect against measles, mumps and rubella.

A mild fever, soreness or a small rash may occur after some live vaccines as the immune system responds. These effects do not automatically mean that the person has the disease the vaccine prevents.

Tell the vaccinating clinician about pregnancy, plans for pregnancy, medicines that suppress immunity, cancer treatment, an organ transplant, immune-system conditions, previous severe vaccine reactions and any recent vaccines. These details can affect whether a live vaccine is suitable now or should be delayed.

After vaccination, follow the clinic's advice, drink enough fluid and monitor how you feel. Keep the vaccine record, including its name and date, because another dose may be scheduled later.

Call emergency services for trouble breathing, swelling of the face or throat, collapse, severe weakness or a widespread rapidly developing rash after vaccination. These can signal a serious allergic reaction and need urgent treatment.

Contact a clinician promptly for a fever that is severe or persistent, unusual bruising, a seizure, marked drowsiness, or symptoms that are worsening rather than settling. Mention the vaccine and when it was given.

Ask whether the proposed vaccine is live attenuated, whether your medicines or health conditions change its timing, which expected reactions apply to that product, and when any later dose is due. If you live with someone whose immunity is severely weakened, ask whether any special precautions apply after the vaccination.