“Surprised there were fewer Covid deaths and serious symptoms in areas where malaria is endemic and natural immunity high (one would expect the opposite), researchers are looking into this.”
Which makes you wonder what the common thread could be.
Shortly after SARS-1 researchers were trying quinine derivative drugs as a means of fighting SARS. Chloroquine was tried in 2005 and found very effective in vitro using green monkey kidney tissue. Chloroquine is a more toxic cousin of HCQ, and SARS-1 of course is the close cousin of Covid-19 aka SARS-2.
I suspect that this 2005 study is probably what prompted Trump’s people to promote HCQ. It held the possibility of working.
But the problem with the 2005 study is that it was done in the lab on monkey tissue in petri dishes. There was no opportunity to try it in people infected with SARS.
That chance finally arrived with Covid 19, and once Chloroquine and HCQ were tried in people they just didn’t work like they had in the lab. Not unusual, just a disappointment. But the conspiracy crowd wouldn’t be deterred by mundane reality and the rest is history.
That doesn’t explain the malaria zone exemption, it just rules out one possibility
Re HCQ, the areas in question are where P. falciparum is resistant to both chloroquine and its kinder cousin HCQ. So it has nothing to do with HCQ.
It’s thought that the people living in these areas who have developed natural immunity to malaria (and nearly all over the age of five have), have immune systems especially attuned to detecting varying foreign proteins and forming defenses in response (trained immunity hypothesis), perhaps including proteins with sequences similar to those expressed by the Covid virus. Certainly they have formed defenses in response to detection varying proteins expressed on the surfaces of P. falciparum by whatever means.
There’s also a theory involving Toll-like receptor 9 (TLR9), but that one gets complicated. TLR7 and TLR8 agonists have already been looked as possible adjuvants for Covid vaccines, and, if I remember correctly, as possible therapies in early stage treatment, again IIRC, including in combo with monoclonal antibodies. TLR9 plays a major role in mediating innate immune response to malaria:
https://www.jimmunol.org/content/188/10/5073
If natural immunity to malaria indeed confers some protection against Covid, the pathways and mechanisms involved (including TLR9) may shed light on possible ways to effectively treat it in the early stage and possible implications for vaccine development.