What is Herd Immunity?

Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease, limiting further spread of the disease. Those who aren’t immune are indirectly protected because ongoing disease spread is reduced.

How is Herd Immunity Achieved?

The percentage of the population that needs to be immune before herd immunity is achieved varies depending on the disease. With diseases that spread easily, a higher percentage of the population needs to be immune for herd immunity to occur.

According to the Journal of American Medicine, about 70-90% of the population needs to be immune to achieve herd immunity. Vaccines are the most common way that herd immunity is achieved, but it can also be reached through prior illness in a community.

Herd Immunity and Vaccines

Vaccines stimulate your body’s immune system to create antibodies against the disease, making you immune to it. If a significant amount of people in a given population are vaccinated, it can create herd immunity to that disease. Achieving herd immunity reduces the spread of a disease, thereby reducing the number of people who can be infected.

Who’s Protected by Herd Immunity?

Put simply, herd immunity protects everyone. Achieving herd immunity reduces the spread of a disease by reducing the number of people who can be infected, which further reduces the spread. In the United States, herd immunity through vaccination has helped make diseases like measles, polio, mumps, and chickenpox rare. 

Herd Immunity and COVID-19

A vaccine for COVID-19, like the one from Pfizer and the soon to be approved vaccine from Moderna, is the best way to achieve herd immunity for the disease. It’s currently estimated that 50-80% of the U.S population will need to be vaccinated to reach the herd immunity threshold. 

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More Questions About Herd Immunity and Vaccines?

If you’d like to learn more about herd immunity, COVID-19 vaccines, or have questions about the vaccines currently available, visit the CDC


Next Steps and Useful Resources:

Understanding the Two Types of COVID-19 Tests
Why Does the COVID-19 Vaccine Require Two Shots?
[PODCAST] COVID-19 CEO Update (12.11.2020)
Find a COVID-19 Testing Site

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