Which statement correctly contrasts innate and acquired herd immunity?

• A. Innate resistance is due to factors other than prior exposure or immunization; acquired resistance develops protective immunity from exposure or vaccination.
• B. Innate resistance requires vaccination; acquired resistance requires prior exposure.
• C. Innate resistance is only present in juveniles; acquired only in adults.
• D. Innate and acquired immunity are the same concept.

Answer: (A)

Innate immunity provides immediate, nonspecific defense that does not depend on prior exposure or vaccination, while acquired (adaptive) immunity is specific to a pathogen and develops after exposure or immunization, building memory for faster responses in the future. The correct statement reflects this: innate resistance arises from factors other than prior exposure or immunization, whereas acquired resistance develops protective immunity from exposure or vaccination. This distinction means vaccines enhance population protection by creating acquired immunity, while innate defenses are always present and not shaped by vaccination. The other ideas—that innate requires vaccination, that innate is only in one age group, or that the two are the same—do not fit the true differences between innate and acquired immunity.