The statement in this thread's title may be true, IF the hypothesis discussed below proves to be right.
The hypothesis goes like this. COVID-19 is a member of a family of coronaviruses, and those other ones aren't as deadly as it is. But when we catch one of those other ones, we develop antibodies to it that also work against COVID--19, because of family resemblance. (This is called cross immunity). So, catching one of COVID-19's "sister" viruses means you will be protected against COVID-19 itself.
From the article:
"Ever since it became apparent that children were less vulnerable to COVID-19 early in the pandemic, scientists have speculated that the regular spread of benign viruses in places like schools could have bolstered their immune response to the latest coronavirus ... Now the idea of "cross immunity" among the broader population is gaining some ground."
"(Because of) an "intriguing" lack of an immediate resurgence in COVID-19 cases following the easing of lockdowns in several countries ... a proportion of the population might have pre-existing immunity to #SARSCoV2, potentially due to prior exposure to 'common cold' coronaviruses."
" ... an American study in the journal Cell suggested between 40 and 60 percent of the population could be immunized against COVID-19 without ever being exposed to it ... Researchers put this down to the action of protective cells, known as T lymphocytes, that had been activated by other coronaviruses responsible for colds."
" ... the threshold (for herd immunity) might be reached when just 10 to 20 percent of the population has been infected."But of course the article goes on to state, and rightly so, that as intriguing as this is, there is as of now no firm evidence that this is really what is happening, and it remains only a hypothesis at this point.
But if the hypothesis is true, it suggests that when the "regular" cold and flu season starts in the coming months, then when a large number of people contract and gain immunities to the
other less lethal coronaviruses, then that acquired immunity may also protect against COVID-19. Thus, the predicted "second wave" of COVID-19 may be much less severe than has been anticipated, because of the cross immunity protection that will be going on at that time.
This is all very interesting, but it does seem to suggest that a "natural experiment" will be taking place during the coming months, during the upcoming cold and flu season, when the second COVID-19 will occur. Or it won't.
If it doesn't occur, that will suggest that maybe there really is something to the cross immunity hypothesis discussed above and maybe that herd immunity could be possible after all.
Article:
https://medicalxpress.com/news/2020-05-coronavirus-centre-immunity.html