Due to the COVID-19 pandemic, we are all very familiar with terms such as confinement, physical distancing, close contact, and quarantine. Here’s another one that’s more fun to talk about:
Immunity to the home.
“A better term for this is population immunity,” said Lori Grooms, director of Infection Prevention and Control for OSF HealthCare.
But herd immunity is more fun to say. It’s easier than stating the immunity of the lyrical community. And we could use a little fun. So for this pandemic lingo lesson, we’ll stick with the pack.
Immunity kills virus targets
Either way, herd immunity is a good thing.
“When we have herd immunity, it means that a good part of the population is immune to disease,” Lori said. “If I am immune as an individual, I will not develop the infection if I am exposed to it. So if a high percentage, say 70%, are immune, that other 30% is less likely to come into contact with someone who has the disease. “
To illustrate, think of your community as a forest where people are prey and viruses are hunters. As people become immune, they disappear from sight.
Eventually, the virus runs out of easy targets.
Some examples of diseases to which our national population has developed herd immunity:
Smallpox is considered eradicated from the planet and polio eliminated in the United States. We still see limited outbreaks of the other diseases on that list, but that’s largely because some people don’t get vaccinated.
Why Vaccines Are Critical
As individuals, our bodies develop immunity against a specific virus or disease in two ways. Either we get sick and develop a natural immunity when we recover, or we get vaccinated.
The duration of immunity can vary with each virus. For example, most people who get measles are immune for life, but you can get the flu every year. Vaccines help protect people who do not have natural immunity, but few vaccines provide lifelong immunity, so we need an annual flu shot.
COVID-19 is caused by a coronavirus similar to the virus that causes the flu.
“There are two factors to consider when we talk about herd immunity,” Lori said. “One is the percentage of the population that needs to develop immunity to control the disease. The other is how long immunity lasts. “
With a highly contagious virus, like SARS-CoV-2 that causes COVID-19, the percentage should be high, probably 70% to 80%, Lori said. Additionally, research to date indicates that once people have had COVID-19 and recovered, their natural immunity lasts for three to nine months.
“That’s why we need the vaccine,” Lori said. “When you have a very, very contagious disease like this, you need a larger part of the population to be immune in order to control it. We need such high percentages that we would never develop herd immunity naturally. You would have to have a large percentage of the population that is reinfected every three to nine months.
“The vaccine will allow more people in the population to develop that immunity. We do not yet know how long immunity due to the vaccine will last. But even if that means getting vaccinated annually, it is no different than getting your annual flu shot. “