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A-Level Biology May/June 2024 Q2(c): Apart from being cost effective, suggest and explain the advantages of using the BCG va…
A-Level Biology · Paper 9700/22 · May/June 2024 · Question 2(c) · [4 marks]
Apart from being cost effective, suggest and explain the advantages of using the BCG vaccine for the prevention and control of TB.
A full-marks model answer with a mark-by-mark examiner breakdown is below.
1 answer
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The BCG vaccine is a live attenuated vaccine. One advantage is that because the bacteria are alive, the cells replicate after administration. [1]
This replication leads to a higher concentration of non-self antigens being presented to the immune system over a period of time. This results in a strong primary immune response, leading to the production of a large number of specific memory cells. [1]
This process confers artificial active immunity to the individual, which is long-lasting. [1]
Due to the strength and longevity of the immune response generated, boosters are not usually required. Furthermore, widespread vaccination helps to establish herd immunity within a population, protecting vulnerable individuals. [1]
How the marks are awarded
- B1 — Stating that the cells in the live vaccine replicate in the body.
- B1 — Explaining that this replication leads to a strong or effective primary immune response.
- B1 — Correctly identifying the type of immunity produced as artificial active immunity.
- B1 — Stating a consequential advantage, such as boosters not being needed, or the establishment of herd immunity.
Common mistakes
- Confusing the type of immunity, for example, stating it provides 'natural active immunity' (which is from infection) or 'passive immunity' (which is from receiving antibodies).
- Failing to mention that the bacteria in the vaccine replicate; this is a key feature of live vaccines that explains their effectiveness.
- Giving vague answers like 'it prevents TB' or 'it creates immunity' without explaining the immunological mechanism involving antigens and a strong response.
- Incorrectly stating that the vaccine contains dead bacteria or toxins, which would be a different type of vaccine with different properties.
Examiner tip: For questions on vaccines, always connect the specific type of vaccine (e.g., live attenuated, mRNA, subunit) to the mechanism and strength of the resulting immune response.
AI-generated model answer, grounded in the official Cambridge mark scheme and reviewed by the MarkScheme team. Mark your own answer to this question →
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