Defining COVID-19 Terms: Herd Immunity

May 6, 2020


Elizabeth (Izzy) Montgomery, MPA
Policy Analyst

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In this installment in our series explaining key terms and phrases used by public health officials in discussions of the COVID-19 pandemic, we look at the term “herd immunity.”

As COVID-19 cases continue to grow in the U.S., the term ”herd immunity has increasingly been cropping up in discussions of the pandemic. Herd immunity is the point at which enough members of a community become immune to an infectious disease to decrease the spread of the disease.

Herd immunity can be achieved when enough members of a community either have recovered from previous infection or have been vaccinated. In order for herd immunity to protect those without individual immunity, a sufficient percentage of people must be resistant to the disease; this percentage is known as the herd immunity threshold.

Public health experts have expressed concerns about misconceptions regarding herd immunity and COVID-19. Infectious disease experts with Johns Hopkins University of Medicine have dismissed claims that herd immunity is being reached in hard hit areas, noting that 70% or more of the population likely would need to become immune to the virus before herd immunity could be reached. Research is ongoing to determine whether a previously infected person develops immunity from the virus, and if so, how long a person maintains that immunity.

As previously stated, vaccines can play a critical role in establishing herd immunity. Although COVID-19 vaccine development efforts are being fast-tracked, and multiple clinical trials are underway, experts estimate that we are at best 18 months away from having a vaccine ready. In the meantime, it is critical that individuals continue to practice social distancing, quarantine if sick, and encourage those at higher risk to stay home if possible.

See more definitions of terms and other information about the pandemic on our website’s COVID-19 in Arkansas page.

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