Cambridge O Level Biology · Syllabus 5090 · Disease and Immunity
Active Immunity
What is Active Immunity?
Defence against a pathogen by antibody production in the person's own body. It develops after infection with the pathogen or after vaccination, involves the person's own lymphocytes, and produces memory cells, so protection is usually long lasting although not necessarily lifelong.
This definition is part of the Disease and Immunity chapter in Cambridge O Level Biology.
Common mistakes with Active Immunity
- "Vaccination gives passive immunity." A vaccine supplies antigens, not antibodies, and your own lymphocytes do the work. Write Vaccination stimulates active immunity: the person's own lymphocytes produce antibodies and memory cells are formed.
Questions students ask about Active Immunity
Why do some vaccines need booster doses if active immunity is long lasting?
Because "usually long lasting" is not the same as permanent. For some pathogens the memory-cell response weakens over years, so a further dose is given to stimulate the response again. This is still active immunity: the person's own lymphocytes do the work each time.
Last reviewed Syllabus 2026-2028