What term describes protection of a population from disease through high vaccination rates?

• A. Quarantine
• B. Herd immunity
• C. Sanitation
• D. Isolation

Answer: (B)

Herd immunity occurs when a large proportion of people in a community are immune to a disease, usually through vaccination. Because so many individuals are not susceptible, the disease has fewer opportunities to spread, which protects the whole population, including those who can’t be vaccinated or don’t have strong immune responses. For highly transmissible diseases, the required vaccination level to achieve this protective effect is very high; when coverage drops, outbreaks become more likely.

The other measures—quarantine, isolation, and sanitation—are important for controlling disease, but they work differently: quarantine and isolation focus on separating people to prevent spread, and sanitation reduces transmission through environmental health measures, not through generating population-wide immunity.