Passive immunization provides immediate protection because pre-formed antibodies are administered. Which of the following statements best reflects this?

• A. Antibodies are available immediately after administration.
• B. The response relies on memory cells.
• C. It induces long-lasting immunity.
• D. It requires weeks to develop.

Answer: (A)

Passive immunization gives immediate protection because the recipient is provided with pre-formed antibodies. Since these antibodies are already present in the bloodstream, they can immediately bind and neutralize pathogens without waiting for the body to generate its own antibodies. This is why protection starts right away. In contrast, relying on memory cells and a stimulated immune response describes active immunization, which builds lasting immunity but requires time to develop. Because there’s no new memory formed with passive transfer, the protection is typically temporary as the administered antibodies are cleared from the circulation. The statement about weeks to develop reflects active immunization dynamics, not passive.