The world has NEVER achieved "natural" herd immunity for other viral diseases that spread easily from person to person, like measles, mumps, chickenpox, and smallpox. Despite being so highly contagious that there was a high likelihood of infection after modest exposure, natural immunity in the human population never got up to a level sufficient to stop those diseases. The term "herd immunity" was only coined AFTER the success of universal vaccination programs. Also note that we have not yet achieved herd immunity to the other common coronaviruses- 4 other types (229E, NL63, OC43, and HKU1-the relatives of SARS-CoV-19) cause many of our colds every year.
David Egilman MD MPH
HIFA Profile: David Egilman is a physician in Attleboro, Massachusetts, USA. He is trained in internal medicine and occupational medicine. He is President of GHETS.org an NGO that supports human resource development in COPC medical and nursing schools in the global South by promoting South-South exchanges. He is a Clinical Professor of Family Medicine at the Alpert School of Medicine at Brown University degilman AT egilman.com