Difference between live and attenuated vaccines

Live means the vaccine uses a microorganism capable of limited replication, rather than only a purified component or an inactivated organism. Attenuated means that the microorganism has been weakened so it can stimulate immune recognition without behaving like its disease-causing form in most healthy people. The immune response can resemble natural exposure, but the vaccine does not suit everyone. The decision depends on age, pregnancy, immune-system conditions, medicines that suppress immunity, and the specific product. MMR, chickenpox, and yellow fever vaccines are examples of vaccines that may use live attenuated formulations.

Tell the vaccinator about pregnancy or possible pregnancy, immune problems, recent vaccines, regular medicines, severe allergies, and previous reactions. Do not skip a recommended vaccine because the word live sounds alarming; ask which formulation is planned and why it is suitable. Childhood immunisation schedules use different vaccine types at different ages, so keep the child's records available and follow the advised timing.

Mild soreness, tiredness, or a low fever can occur after vaccination. Seek urgent medical help for trouble breathing, swelling of the face or throat, collapse, widespread hives, or rapidly worsening illness. Contact a clinician promptly if you are pregnant, severely immunocompromised, or have received a live vaccine despite being told to avoid it, so personalised advice can be given.

Ask whether the vaccine is live attenuated or another type, whether your health conditions or medicines affect eligibility, how to space it from other vaccines, and which reactions require medical attention. For travel, ask whether yellow fever vaccination is relevant to your destination and health history.