Scientists have been working to produce a vaccine for HIV for many years.

How could a vaccine work to prevent a person being infected with HIV?

Write the stages A, B, C, D and E in the correct order. The first stage has been completed for you.

A Antibodies attach to the inactive virus.
B Antibodies destroy the inactive virus.
C An inactive form of the virus is injected into the body.
D If the active virus enters the body, antibodies are produced quickly.
E White blood cells produce antibodies to the inactive virus.

C → ___ → ___ → ___ → ___

Vaccines work by introducing a harmless or inactive form of a pathogen into the body. 1. **C:** An inactive form of the virus is injected. 2. **E:** The body's white blood cells recognise this as foreign and produce specific antibodies against it. 3. **A:** These antibodies then attach to the inactive virus. 4. **B:** The antibodies help to destroy the inactive virus. 5. **D:** Crucially, the immune system now has memory cells. If the person is later infected with the active, live virus, the white blood cells can produce the correct antibodies very quickly and in large numbers, destroying the pathogen before it can cause illness.