What does herd immunity refer to?

Herd immunity refers to the concept where a significant portion of a population becomes immune to an infectious disease, either through vaccination or past infections, thereby offering indirect protection to those who are not immune. When enough individuals are immune, the spread of the disease is limited, making it less likely that susceptible individuals will encounter the pathogen. This phenomenon is crucial in protecting vulnerable populations, such as those who cannot be vaccinated due to medical reasons or those who may not respond adequately to vaccines.

The other context provided does not encapsulate the primary mechanism of herd immunity. The focus is on collective immunity and its benefits to the community as a whole, rather than on individual immunity mechanisms or policies surrounding vaccination mandates. Understanding herd immunity helps emphasize the importance of widespread vaccination in controlling epidemics and maintaining public health.