How is herd immunity achieved?

Herd immunity is achieved when a significant portion of a population becomes immune to a disease, which can occur either through vaccination or previous infections. This immunity helps to protect individuals who are not immune by reducing the overall amount of the pathogen in the community. When enough people are immune, the spread of the disease is minimized, making it less likely for those who are susceptible—such as individuals who cannot be vaccinated due to medical reasons—to come into contact with the virus or bacteria.

The concept relies on the principle that diseases spread more easily when there are more susceptible individuals. By having a substantial percentage of the population immune, the chain of transmission is broken, which ultimately helps to prevent outbreaks. A threshold of immunity, often referred to as the herd immunity threshold, varies by disease but is essential for effective disease control and prevention.