Vaccines and their role · NCERT Biology

What happens when a 'killed' vaccine is injected into the body?

  1. The pathogen begins multiplying inside the liver cells
  2. The immune system detects surface antigens and produces antibodies
  3. The pathogen integrates its DNA into the host cell genome
  4. No immune response occurs because the pathogen is already dead
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Correct answer: The immune system detects surface antigens and produces antibodies

Even though the pathogen is killed and cannot replicate, its structural proteins (antigens) remain intact. The immune system recognizes these foreign proteins and mounts a primary immune response, creating memory for future protection.

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