From what I read, the term, “natural herd immunity” (community immunity/population immunity), has been used for more than a century to reference a point that enough people in an extended area become sufficiently resistant to a disease so that an infectious substance/agent is unlikely to pass from person to person.
This enables even people who do not have natural or acquired immunity to actually become protected by the sheer improbability of a person’s having contact with an infected person.
From my limited experience (not nearly 100 years), vaccinations have been the only route to herd immunity—for example, smallpox vaccinations we received as children and then had repeated later. As far as I knew as a youngster, everyone “got vaccinated” for small pox and had a funny scar at the back of a shoulder. I later learned that to be really sure of herd immunity, 100% have to be immune, but even later, I learned that a level of 90% or more was really safe!
There are two main ways people become immune: having the infection and acquiring immunity or having a vaccination to become immune as the body forms antibodies. I read in the paper and hear on the news reports that, to make our population pretty safe from COVID-19, many scientists are estimating that it will take approximately a 70% immunity level to make things really safe!
However, at this time we do not have an approved vaccine, and I hope 70% or more of our population do not have to experience the actual infection!
So, most spokespeople to whom I have listened strongly urge against depending upon “herd immunity” for the COVID-19 strategy, since it is estimated that only 10% or so of all folks in the United States have antibodies to the responsible virus.
Plus, scientists/doctors are not sure that having the antibodies alone can be counted upon for success, since some people have tested “recovered” from the COVID-19 Virus Infection and then have been apparently re-infected!
The last words I have read recently urge the dependence upon VACCINES, because they can be formulated to produce/trigger stronger immunity levels than natural infections. And, the same words urge taking extra precautions until, and maybe even after, vaccine(s) exist.
Again, I emphasize that I am a reader, listener, discusser, and writer—not a doctor!
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