Non-specific immune benefits of measles vaccine

Steps:

• Identify that the vaccine provides protection beyond measles, indicating non-specific effects on immunity.
• Recall vaccines primarily activate adaptive immunity via B and T cells, but measles vaccine boosts innate responses against other infections.
• Eliminate options claiming specific memory or passive/natural immunity to unrelated pathogens, as these are antigen-specific.
• Select the option linking vaccine-induced cells to broader antibody effects.

Why B is correct:

• Memory cells differentiate into plasma cells that produce antibodies; in this context, anti-measles antibodies provide cross-protection by binding non-specifically to other pathogens, enhancing overall survival per immunological studies on vaccine heterologous effects.

Why the others are wrong:

• A: B-cell memory provides specific active immunity, not passive, and is measles-targeted, not broadly protective.
• C: Identical to B but incomplete; lacks explanation of cross-binding for extra protection.
• D: T-cell memory confers specific adaptive immunity, not "natural" (innate) against unrelated infections.

Final answer: B