Herd immunity is achieved primarily through vaccination. Which statement best describes its benefit?

• A. It protects only the vaccinated
• B. It has little impact on disease spread
• C. It protects those who cannot be vaccinated by reducing transmission
• D. It ensures that everyone will be immune

Answer: (C)

Herd immunity works by stopping transmission chains when a large portion of the community is immune. That creates a barrier that makes it much harder for the pathogen to move from person to person. The key benefit is indirect protection for people who cannot be vaccinated or for whom vaccines are less effective—such as the immunocompromised, very young, or those with certain medical conditions—because the pathogen has fewer opportunities to spread to them. When enough people are immune, fewer people to pass the infection to means the risk to these vulnerable individuals drops substantially, even if they themselves aren’t immune.

The other statements miss this essential point: herd immunity isn’t limited to protecting only the vaccinated, it does reduce disease spread, and it doesn’t guarantee that everyone becomes immune.