Active immunity can be acquired by which method?

• A. It can be acquired by contracting the disease or through vaccination.
• B. It is acquired exclusively through vaccination.
• C. It is always maternally derived.
• D. It is never long-lasting.

Answer: (A)

Active immunity develops when the body's immune system encounters an antigen and actively responds, producing specific antibodies and memory cells that provide long-lasting protection. It can be acquired through natural infection, where the person fights off the disease and builds memory, or through vaccination, which trains the immune system without causing the disease. This is why the best answer is that active immunity can be acquired by contracting the disease or through vaccination.

The other statements don’t fit because active immunity is not limited to vaccination alone—natural infection also creates active immunity. It’s not always maternally derived; maternal antibodies provide passive immunity to a newborn, which wanes over time and does not involve the child’s own adaptive immune memory. And active immunity is not never long-lasting; it often lasts for years or lifetime due to memory cells, though some vaccines may require boosters.