A major advantage of passive immunization compared to active immunization is that

• A. Antibody is available more quickly
• B. Antibody persists for the life of the recipient
• C. IgM is the predominant antibody class provided
• D. Oral administration can be used

Answer: (A)

Providing pre-formed antibodies gives protection right away, since there’s no need for the recipient’s immune system to respond and generate antibodies. This immediate availability is crucial in scenarios like exposure to a toxin or a contagious pathogen, where every hour counts. In contrast, active immunization requires time for the body to mount an immune response and develop memory, so protection isn’t immediate and depends on how quickly the adaptive response develops. Because the protection from passive immunization comes from antibodies that will gradually be cleared, it is temporary and does not create lasting immune memory. The antibody products used are typically given by injection and are mainly IgG, not IgM, and oral administration isn’t reliable because proteins would be broken down in the digestive tract, preventing systemic protection.