Which is an example of passive immunity used in clinical practice?

• A. Vaccination with inactivated virus
• B. Live attenuated vaccine
• C. Natural infection
• D. Monoclonal antibody therapy

Answer: (D)

Passive immunity involves giving ready-made antibodies to someone else, providing immediate protection without the recipient’s immune system having to respond. Monoclonal antibody therapy fits this precisely: patients receive specific antibodies that bind a pathogen or toxin, neutralizing it or guiding its destruction. The protection arrives quickly but is temporary because these antibodies are cleared from the body, and the recipient does not develop their own lasting memory.

In contrast, vaccinations with inactivated or live attenuated viruses, and natural infection, all trigger active immunity by stimulating the person’s own immune system to produce antibodies and memory cells, which takes time to develop but tends to be longer-lasting.