What is the definition of "herd immunity"?

The definition of "herd immunity" is accurately described as the scenario when a large portion of a community becomes immune to a disease, leading to a reduction in its spread. This immunity can be achieved through vaccination or past infections within the community. When a significant percentage of the population is immune, the chances of the disease spreading are diminished, offering protection to individuals who are not immune, such as those who cannot be vaccinated for medical reasons.

Herd immunity is crucial for controlling infectious diseases, as it helps safeguard the entire community's health. By lowering the number of susceptible individuals, the likelihood of outbreaks decreases, which is especially important for protecting vulnerable populations.