As the new coronavirus continues to spread around the world, you have probably heard health experts talk about herd immunity as a way to control the virus. But what the hell is group immunity and how does it work? This is what you need to know.
The 112 on collective immunity
When you think of immunity, you probably think of something like chickenpox. Once you have had the red spots, you cannot have them again. In other words, you are immune. And as a bonus, you can't pass the disease on to anyone else.
Of course, if everyone in a community is immune to an infectious disease, it cannot spread. But it turns out that you can stop the spread of disease without everyone being immune. Collective immunity is when most people in a community are immune to a specific infectious disease.
Like all life forms, a virus wants to produce more viruses. The only way to do this is to go from someone infected to someone who is not infected and is therefore not immune. If you are immune and the virus leaps from me to you, the virus will not spread.
That is, if there is widespread immunity, the virus has nowhere to go and eventually disappears.
Why is group immunity important?
Collective immunity not only helps stop the spread of infectious diseases, but it creates a protective ring around people scattered within the community who are not immune. Think of immunity as a field of social force against disease.
It is particularly important for people with weak immune systems who can develop an infection more easily or who cannot be vaccinated. This includes older adults, people with conditions like diabetes or heart disease, pregnant women, and babies.
How is collective immunity achieved?
There are two main ways to develop collective immunity:
Naturally
The community can develop natural immunity. When you get sick, your body develops antibodies to fight the infection. Your body retains these antibodies, so it is ready to fight the disease in case you find it again.
With vaccines
Vaccines can also help develop immunity in people. A vaccine mimics infection and tricks your body into making antibodies.
The exact moment in which the group's immunity comes into play depends on how contagious the virus is or on its reproduction number.
So if the reproduction number is two, that means that an infected person will transmit the diseases to two people as long as they are contagious. The higher the reproduction number, the more contagious the disease is, and most of the community needs to be immune to stop the spread.
What if group immunity cannot be achieved?
When group immunity is broken, a hot spot can develop in a community. For example, in recent years we have seen outbreaks of highly contagious diseases such as measles, which has a reproductive number between 12 and 18. Measles requires a collective immunity between 93 and 95 percent of the population. When immunity to measles in the community falls between that critical number, the disease can start to spread like a hot potato.
For diseases that have a vaccine, the best thing you can do to ensure the health and safety of your community is to get vaccinated. And stay up-to-date on vaccinations too. For some diseases, immunity can decrease after a certain period of time, so it is important to keep the force field intact. (That's why you need to get a flu shot every year.)
If there is still no vaccine, as in the case of COVID-19, it is a little more complicated. COVID-19 requires that 60 to 70 percent of the community population be immune to achieve collective immunity . However, relying on natural immunity can cost many lives.
That is where the home shelter and social distancing regulations come into effect. We are trying to do what makes sense to save as many lives as we can until we get to collective immunity. At the end of all this, the hope is that we have a safe and effective vaccine and that we have lost the minimum number of lives.
Collective immunity is the responsibility of an individual and the community as a whole. We have a responsibility to ourselves to protect ourselves. But we also have a responsibility to others in our community.
