Which statement is true about inactivated vaccines and subunit vaccines?

• A. Inactivated vaccines use live pathogens that have been weakened.
• B. Inactivated vaccines use killed pathogens; subunit vaccines use only specific antigenic components.
• C. Inactivated vaccines use killed pathogens; subunit vaccines use whole, intact pathogens.
• D. Subunit vaccines use cytokines as the active component.

Answer: (B)

The key idea is how these vaccines present antigens to the immune system. Inactivated vaccines use pathogens that have been killed, so they can’t replicate, but their antigens remain to stimulate immunity. Subunit vaccines include only specific antigenic components of the pathogen—such as a protein or polysaccharide—without exposing the person to the whole organism. That makes the statement true: inactivated vaccines use killed pathogens, and subunit vaccines use only specific antigenic components. The other descriptions mix up concepts—live attenuated vaccines use weakened live organisms, subunit vaccines don’t include whole pathogens, and cytokines aren’t the usual active component in subunit vaccines.