The Certification Study Guide (6th edition) defines passive immunity as protection that results from the administration of preformed antibodies, rather than stimulation of the individual’s own immune system. Passive immunity provides immediate but temporary protection, because the recipient does not produce antibodies and therefore does not develop immunologic memory.

Tetanus antitoxin is a classic example of passive immunity. It contains antibodies that neutralize tetanus toxin directly and is used in situations where immediate protection is needed, such as after certain wounds in individuals with unknown or inadequate vaccination history. The study guide emphasizes that passive immunization is particularly important in post-exposure management when waiting for an active immune response would be too slow to prevent disease.

The other options represent active immunization, not passive immunity. Vaccines such as hepatitis B vaccine, influenza vaccine, and human diploid cell rabies vaccine stimulate the recipient’s immune system to produce its own antibodies and immune memory. While rabies immune globulin provides passive immunity, the rabies vaccine itself is an active immunizing agent.

This distinction between active and passive immunity is a frequently tested CIC exam concept, especially in the context of occupational health, post-exposure prophylaxis, and immunization programs. Recognizing that passive immunity involves antibody products (antitoxins or immune globulins) rather than vaccines is essential for accurate infection prevention decision-making.