Which statement distinguishes inactivated from live vaccines?

• A. Live vaccines use weakened organisms
• B. Inactivated vaccines use dead organisms; live vaccines use weakened organisms
• C. Inactivated vaccines use live organisms
• D. Inactivated vaccines require boosters yearly

Answer: (B)

Understanding this distinction helps you see why the statement is correct. Inactivated vaccines contain organisms that have been killed; they cannot replicate in the body, so the immune system sees pieces of the pathogen rather than an active invader. This often leads to a weaker or more short-lived immune response, which is why many inactivated vaccines require multiple doses and sometimes adjuvants to boost immunity. Live vaccines, on the other hand, contain attenuated, or weakened, organisms that are still alive and can replicate to some extent. This replication tends to provoke a stronger and longer-lasting immune response, usually with fewer doses, but it carries a small risk for people with severely weakened immune systems.

So the defining distinction is that inactivated vaccines use dead organisms, while live vaccines use weakened, live organisms. The other statements don’t capture this core contrast or make inaccurate claims about how these vaccines work or how often boosters are needed.