Why is live attenuated vaccine used in yellow fever vaccination?

A live attenuated vaccine contains a weakened form of the virus. It can prompt the body to make immune defences, including antibodies and immune memory, while being too weakened to produce yellow fever in a healthy person who is suitable for vaccination. That immune memory helps the body respond more quickly if it later encounters the yellow fever virus. Vaccination is preventive care; it does not treat an active yellow fever illness.

Suitability matters because a vaccine that contains a weakened live virus may not be appropriate for everyone. Age, pregnancy or breastfeeding, immune-system conditions, medicines that suppress immunity, allergies, and previous vaccine reactions can all affect the advice you receive.

Arrange a travel-health or clinical appointment early enough to discuss your destination, transit points, medical history, and any entry documentation that may be needed. Bring a list of medicines and details of prior vaccinations. Follow the clinician's advice about the vaccine product, timing, and any observation after vaccination.

You can read more about the vaccine itself in Yellow Fever Vaccination and about the vaccine type in Live Attenuated Vaccine.

Seek urgent medical help for trouble breathing, swelling of the face or throat, widespread hives, severe weakness, confusion, or collapse after a vaccination. Contact a clinician promptly if you develop a concerning reaction, fever with worsening illness, or symptoms that worry you after returning from an area where yellow fever occurs.

Ask whether your travel itinerary makes yellow fever vaccination advisable or required, whether any health condition or medicine changes your eligibility, and what reactions should prompt a call for advice. If you cannot receive a live vaccine, ask how to reduce exposure to mosquito bites and whether travel documentation options apply.