A polyvalent vaccine is sometimes called a multivalent vaccine; which statement is true?

• A. It protects against a single disease.
• B. It protects against multiple diseases.
• C. It is ineffective in some species.
• D. It requires no booster.

Answer: (B)

Polyvalent vaccines are designed to protect against more than one disease (or multiple strains of a pathogen) in a single preparation. That’s why they’re also called multivalent vaccines. The true statement reflects this broadened coverage: one shot targets several diseases, not just one.

The other ideas aren’t defining features of polyvalent vaccines. A single-disease protection describes monovalent vaccines, not polyvalent ones. Whether a vaccine works in different species isn’t a property of being polyvalent itself—it's about the specific product’s design and how different species respond to it. And whether a booster is required depends on how long the immune response lasts for that particular vaccine, not on the fact that it is polyvalent.