Certification Board of Infection Control and Epidemiology (CBIC) Practice Exam 2025 – The All-in-One Guide for Exam Success

Herd immunity refers to the concept of collective resistance to infection within a population. This phenomenon occurs when a significant portion of the community becomes immune to a specific infectious disease, either through vaccination or previous infections. When a large percentage of the population is immune, the spread of the disease is limited, thereby protecting those who are not immune, such as individuals who cannot be vaccinated due to medical reasons or those who are more susceptible to severe illness. This collective immunity is crucial for controlling outbreaks and ensuring public health.

The other options do not capture the essence of herd immunity. While the notion of only a few needing protection suggests a misunderstanding of how infection control works at the community level, the focus on individual immunity highlights personal rather than collective health. The idea of vaccines being effective if applied randomly misrepresents how herd immunity is achieved through widespread vaccination efforts within a population rather than arbitrary or uneven applications.