Herd immunity

Definition

Herd immunity is a form of indirect protection from infectious diseases that occurs when a sufficient percentage of a population becomes immune to an infection, thereby reducing its spread. It can be achieved through vaccination or previous infections.

5 Must Know Facts For Your Next Test

1. Herd immunity helps protect individuals who cannot be vaccinated due to medical reasons.
2. A high vaccination coverage in the community is essential to achieve herd immunity.
3. Herd immunity thresholds vary for different diseases; for measles, it requires about 95% of the population to be immune.
4. When herd immunity is achieved, chains of infection are disrupted, making outbreaks less likely.
5. Herd immunity does not apply to all infectious diseases, particularly those that do not spread human-to-human.

Review Questions

• What is the primary way to achieve herd immunity in a population?
• Why is herd immunity important for individuals who cannot receive vaccines?
• What is the approximate herd immunity threshold for measles?

Related terms

Vaccination: The administration of a vaccine to help the body develop immunity against a specific disease.

Immunization: The process by which an individual becomes protected against a disease through vaccination.

Infectious Disease: Diseases caused by pathogenic microorganisms such as bacteria, viruses, parasites or fungi that can spread directly or indirectly from one person to another.