Herd immunity

Definition

Herd immunity occurs when a large portion of a population becomes immune to a disease, making the spread of the disease from person to person unlikely. This can be achieved through vaccination or past infections.

5 Must Know Facts For Your Next Test

1. Herd immunity protects those who cannot be vaccinated, such as newborns or individuals with compromised immune systems.
2. The threshold for herd immunity varies depending on the disease and its transmissibility (R0 value).
3. Vaccination is a critical tool in achieving herd immunity for many infectious diseases.
4. Herd immunity does not mean that everyone in the community is immune, but enough people are resistant to prevent widespread outbreaks.
5. The concept of herd immunity was first recognized in relation to measles control efforts in the early 20th century.

Review Questions

• What are two primary ways in which herd immunity can be achieved?
• Why is herd immunity particularly important for protecting vulnerable populations?
• How does the R0 value of a disease affect the threshold needed for herd immunity?

Related terms

Vaccination: A biological preparation that provides active acquired immunity to a particular infectious disease.

R0 (Basic Reproduction Number): A measure of how many people, on average, one infected person will pass the virus onto.

Adaptive Immunity:

The body's ability to recognize and defend itself against specific pathogens through immunological memory.