Question: How do vector vaccines work to provide immunity? (BPSC 69th Q.No. 22)

(A) By introducing a weakened or inactivated virus into the body
(B) By directly attacking and destroying pathogens in the body
(C) By placing the virus in a modified version of a different virus
(D) By entering directly into the cells and enabling them to create spike proteins

Correct Answer: (C) By placing the virus in a modified version of a different virus Explanation in Simple Sentences:

• Option (A): Weakened or inactivated viruses are used in traditional vaccines, like polio or measles vaccines. Vector vaccines don’t use the actual target virus; they use a harmless virus to carry genetic material. This is incorrect.
• Option (B): Vaccines don’t directly attack pathogens. They train the immune system to recognize and fight pathogens later. This is incorrect.
• Option (C): Vector vaccines use a harmless virus (the vector, like adenovirus) to carry a piece of genetic code from the target virus (e.g., SARS-CoV-2). The vector delivers this code to cells, which produce a viral protein (like the spike protein) to trigger an immune response. This is correct.
• Option (D): This describes part of the process but is incomplete. Vector vaccines don’t enter cells directly; the vector virus carries the genetic material into cells to make spike proteins. This is partially correct but not the full mechanism, so it’s incorrect.

Reason: Vector vaccines work by using a modified, harmless virus (vector) to deliver genetic instructions from the target virus into human cells. These cells produce a viral protein, triggering the immune system to build immunity without causing disease. Option (C) best describes this process.

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Key Terms Explained:

• Vector Vaccine: A vaccine that uses a harmless virus (vector) to deliver genetic material from a pathogen to stimulate immunity. Example: AstraZeneca’s COVID-19 vaccine uses an adenovirus vector.
• Immunity: The body’s ability to fight off a specific pathogen by recognizing it and responding with antibodies or immune cells.
• Virus: A microscopic infectious agent that replicates inside host cells. In vector vaccines, the target virus’s genetic code (not the whole virus) is used.
• Vector: A modified, harmless virus (e.g., adenovirus) that carries genetic material into cells without causing disease.
• Genetic Material: DNA or RNA that codes for a specific protein, like the spike protein of SARS-CoV-2, which triggers an immune response.
• Spike Protein: A surface protein on some viruses (e.g., SARS-CoV-2) that the immune system recognizes. Vector vaccines instruct cells to produce this protein to train the immune system.
• Immune Response: The body’s reaction to a foreign substance, involving antibodies and immune cells (like T-cells) to fight infection.
• Antibodies: Proteins produced by the immune system to neutralize specific pathogens.

How Vector Vaccines Work (Detailed):

1. A harmless virus (vector, e.g., adenovirus) is modified to carry a gene from the target virus (e.g., SARS-CoV-2 spike protein gene).
2. The vector enters human cells and delivers the gene.
3. Cells use the gene to produce the viral protein (e.g., spike protein).
4. The immune system recognizes the protein as foreign, producing antibodies and T-cells.
5. This trains the immune system to recognize and fight the real virus if exposed later, providing immunity without causing illness.

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Five Probable Questions of Similar Difficulty

1. Question: What is the role of the vector in a vector vaccine?
   (A) Directly destroys the pathogen
   (B) Carries genetic material into cells
   (C) Weakens the target virus
   (D) Produces antibodies
   Answer: (B) Carries genetic material into cells
   Explanation: The vector (e.g., adenovirus) delivers the target virus’s genetic code into cells to trigger an immune response.
2. Question: Which component of a virus is commonly used in vector vaccines to stimulate immunity?
   (A) Entire virus
   (B) Spike protein gene
   (C) Virus capsule
   (D) Whole pathogen
   Answer: (B) Spike protein gene
   Explanation: Vector vaccines carry the gene for a viral protein (like the spike protein) to make cells produce it and trigger immunity.
3. Question: How do vector vaccines differ from mRNA vaccines?
   (A) Use a live virus
   (B) Use a vector to deliver genetic material
   (C) Contain inactivated virus
   (D) Directly produce antibodies
   Answer: (B) Use a vector to deliver genetic material
   Explanation: Vector vaccines use a harmless virus to deliver DNA, while mRNA vaccines deliver RNA directly to cells.
4. Question: What does the immune system produce in response to a vector vaccine?
   (A) New viruses
   (B) Antibodies and T-cells
   (C) Weakened pathogens
   (D) More vectors
   Answer: (B) Antibodies and T-cells
   Explanation: The immune system produces antibodies and T-cells to recognize the viral protein made by cells.
5. Question: Why don’t vector vaccines cause the disease they protect against?
   (A) They use the whole virus
   (B) They use a harmless vector
   (C) They contain inactivated virus
   (D) They block immune responses
   Answer: (B) They use a harmless vector
   Explanation: The vector is modified to be harmless and only carries a gene, not the disease-causing virus.

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Preparation Strategies for 71st BPSC Prelims

• Study vaccine types (vector, mRNA, inactivated) and their mechanisms.
• Understand key terms like vector, immunity, and spike protein.
• Practice questions on how vaccines stimulate the immune system.
• Review examples like AstraZeneca or Johnson & Johnson’s COVID-19 vaccines.
• Avoid confusing vector vaccines with traditional (inactivated) or mRNA vaccines.