Understand what's known about herd immunity and what it means for Coronavirus disease 2019 (COVID-19)

Understand what's known about herd immunity and what it means for Coronavirus disease 2019 (COVID-19):

A lot of people have started talking about Herd immunity as a possible solution to the Covid 19 crisis.

First, properly understand what is Herd immunity.

Understand how herd immunity works and what experts are saying about its potential impact on the COVID-19 pandemic.

Why is herd immunity important?

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely.

As a result, the whole community becomes protected — not just those who are immune.

Often, a percentage of the population must be capable of getting a disease in order for it to spread. This is called a threshold proportion. If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold.

What percentage of a community needs to be immune in order to achieve herd immunity?

It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread.

There are two paths to herd immunity for COVID-19 — vaccines and infection.

Vaccines

A vaccine for the virus that causes COVID-19 would be an ideal approach to achieving herd immunity. Vaccines create immunity without causing illness or resulting complications. Herd immunity makes it possible to protect the population from a disease, including those who can't be vaccinated, such as newborns or those who have compromised immune systems. Using the concept of herd immunity, vaccines have successfully controlled deadly contagious diseases such as smallpox, polio, diphtheria, rubella and many others.

Natural infection

Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection.

However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID-19. First, it isn't yet clear if infection with the COVID-19 virus makes a person immune to future infection.

For Covid

Even if infection with the COVID-19 virus creates long-lasting immunity, a large number of people would have to become infected to reach the herd immunity threshold. Experts estimate that in the U.S., 70% of the population — more than 200 million people — would have to recover from COVID-19 to halt the epidemic. If many people become sick with COVID-19 at once, the health care system could quickly become overwhelmed. This amount of infection could also lead to serious complications and millions of deaths, especially among older people and those who have chronic conditions.