Herd Immunity and COVID-19: What You Need to Know

A group of people gathering outdoors in Texas

As the COVID-19 pandemic continues and vaccinations are rolling out worldwide, there’s talk about “herd immunity”. How might we be able to achieve it in an effort to fight off COVID-19? Let’s dig into the specifics of what herd immunity means, and how it relates to COVID-19.

What is herd immunity?

Herd immunity is a term that is used when a large percentage of a population becomes immune to a certain infectious disease. Then—because those who are immune will not transmit the illness—the transmission rate is lowered, stopping the spread. Herd immunity is also sometimes referred to as community immunity, population immunity, or herd effect. There is more than one way that herd immunity can be achieved. It can happen through direct exposure and prior illness to the infectious disease, through being vaccinated against the disease, or through a combination of these two factors.

What exactly is immunity?

Immunity refers to a state where humans can resist an infection through the creation of antibodies which eliminate the “threat.” The way that immunity is achieved after infection is due to your body’s creation of antibodies generated to specifically fight that infection, then retaining those antibodies as further protection afterwards in case that illness appears again. Immunity is achieved through vaccination in a similar fashion, though instead of becoming infected, the vaccine effectively teaches your immune system how to create these antibodies without actually having to be exposed to the disease. Depending on many factors, people may stay immune to certain diseases for only a certain amount of time, or for life. At this time, the length of immunity towards COVID-19 either through previous contraction the virus or through vaccination is not fully known.

How many people need to be immune before herd immunity is achieved?

Though it depends on the ease with which an infectious disease is spread, in general herd immunity requires that 70-80% of a community be immune to protect all. More specifically, researchers and medical professionals calculate a threshold which needs to be achieved before a decline in the transmission of an infection is observed, and this threshold is reached when each person who contracts a disease passes it on to less than one person, on average. If a disease spreads easily, it could require more of the population to be immune before herd immunity is achieved.

Is it good to be exposed to COVID-19 to become immune?

Because COVID-19 carries a significantly high risk for those who are exposed, it is not recommended to seek intentional exposure to obtain immunity. This may be a technique that is familiar from other infectious diseases such as chickenpox. However, herd immunity through vaccination is a much safer option due to the risks associated with contracting the disease. In addition, the idea to expose a younger and less at-risk population to COVID-19 with the hope of creating herd immunity creates a very high risk for more vulnerable people as the disease becomes widespread. Due to the unpredictability and very high risk of this approach, it is much preferable to attempt to achieve herd immunity through widespread vaccination. To learn more about how COVID-19 vaccines work, check out our previous article Answers to Your Top COVID-10 Questions.

Why is herd immunity important?

Beyond the importance of stopping the spread of an infectious disease, herd immunity is important because not every member of a population can be protected through vaccination. Depending on the disease in question, younger children and babies, people who are pregnant, those with weakened immune systems, and others at high risk due to different circumstances may not be able to safely receive a vaccine. Fostering herd immunity helps keep those safe who are more vulnerable due to their lack of individual immunity. 

How many people need to be vaccinated before we have herd immunity from COVID-19?

Because COVID-19 is new and information about immunity generally is limited, we don’t know exactly when or if herd immunity could be achieved. To better predict the possibility of creating herd immunity from COVID-19, we first need to know more about how long immunity lasts in individuals who have been exposed to the virus or who have been vaccinated. Other factors—including variants of the virus—make herd immunity even more difficult to predict; both the higher rates of transmission seen in COVID-19 variants and the rate at which new variants are appearing counteract the potential for herd immunity.

Today, certain viruses change so quickly and are spread so easily that herd immunity is never effectively achieved. One of the most common examples of this is the flu, where we see new strains appearing perpetually. This makes it impossible for an entire population to become effectively immune before people are reinfected with a new strain.

Can herd immunity totally eliminate certain diseases?

Though rare, if herd immunity is maintained for long enough, eventually there could be a transmission rate of zero. This effectively eliminates the disease. When this happens worldwide, diseases can be declared eradicated. Currently, only two diseases have been declared eradicated worldwide, smallpox and rinderpest.

Can I get back to regular life once I’m vaccinated?

The world is still learning about how long COVID-19 vaccines protect individuals. Because some of the population is still not immunized, those who have been vaccinated must still follow public health guidelines. This includes wearing a mask in public and maintaining physical distancing, frequent hand-washing, avoiding large public gatherings, and all other recommendations relevant to your jurisdiction. Certain details are still unknown about the transmission of COVID-19. This includes whether it could be transmitted by those who have been vaccinated, and other risk factors that we simply do not know the answers to yet. The best course of action according to stop the pandemic is to vaccinate as many people as possible. This will ensure the safety of as many people as possible.

COVID-19 testing

The spread of COVID-19 is being slowed is through frequent testing and monitoring of the disease. Through antibody or serology testing, we also learn more about the behaviour of this virus. Your Health Lab offers COVID-19 surveillance testing, PCR testing, and antibody testing. These help individuals and institutions monitor and stop the spread of COVID-19. Check out our offerings and learn all about our COVID-19 testing here.


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