This is another in the emerging line of studies building epidemic models with some capability to account for variation in susceptibility to infection. (Arxiv Paper) The authors explain how something called dynamic causal modeling could be used to adjust models based on findings from immune response studies and surveys and the resulting variation in susceptiblility. A pretty theoretical paper but interesting information on the level of variability in immune response and the impact on epidemic course.
This study looked for antibody prevalence among schoolchildren in Switzerland. (Medrxiv Paper) They found a prevalence of about 3%, which was similar to the community rate. No clusters were found. The rate was much higher than that shown by PCR testing, in fact 90 times higher.
Researchers keep looking for associations between risk of infection and various factors. This brief article summarizes findings on blood type, saying there may be a link between cases and blood type, but not severity of disease. (JAMA Article)
Blood donations may be a way to test for antibody prevalence and a couple of studies have done that. Here is another one, from the Red Cross across most of the country. (JAMA Article) Over 950,000 donations were tested, less than 2% were positive. Rates increased throughout the study period. Blood donors may be less likely to have been sick with CV-19. A similar result was reported by another blood collection firm in another paper. (Medrxiv Paper)
Do antibody tests perform uniformly across sub-populations? This study looked at the question. (Medrxiv Paper) And in fact differences were found by sex, age and minority status. The study was comparing antibody results to positive PCR test results, so false PCR positives would have made the antibody test appear less accurate. But the variability across populations and tests would remain.
And here is a letter from doctors in Belgium who think that the reaction to the epidemic has been unbalanced and damaging. Thanks to a reader for sending the link and it is worth a read. (Belgium Letter) I tend to agree with every argument they make, particularly about the lack of balance in considering lives other than those of CV-19 patients.
This study talked about the potential effects of co-infection of CV-19 and influenza. (Medrxiv Paper) The study comes from England. The researchers found about 58 cases of co-infection in over 19,000 patients. Older patients tended to be more likely to be co-infected. There was some evidence of viral competition as influenza patients tended to be less likely to have a CV-19 infection than were patients overall. But when co-infection did occur it was associated with more severe disease.
The Healthy Skeptic is a website about the health care system, and is written by Kevin Roche, who has many years of experience working in the health industry. Mr. Roche is available to assist health care companies through consulting arrangements through Roche Consulting, LLC and may be reached at 
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The aby tests all measure IgG whereas there are 2 other and very important elements in immunity: IgA abys and T cell response, especially IL 2. Any so called studies re “immunity” are quite superficial without these added elements. In our clkinic, eg, when testing for borrelia (Lyme) or babesia and bartonella “persistence (Lyme coinfections) we do all the T cell studies — far more accurate and critical in determining status. Of course our wonderful Mayo Clinic has no idea what these are, and so they continue to be the WORST place to go if one has Lyme. Here, vaccination — which produces only the IgG aby — does not equal immunization by any stretch. So, her immunity or natural infection in the community, is the only way to suppress the infection. Reducing the attendant morbidity and mortality is a combination of protection for the medically vulnerable and resilience for everyone else. Here is the discussion of resilience and how to confer it:
https://minnesotanaturalmedicine.com/blog/the-path-to-resilience/
Overhearing as I do, conversations about Covid and the higher ed business, I see no evidence of ANY recognition that this virus has played itself out- most collegesare planning for I dunno what, a third, fourth fifth wave of “cases”? A huge % of Americans are still all in on the panic. It can only be described as mass insanity, with no end in sight. No end to the lockdowns (not that they were ever needed), the masking, the social distancing (God I hate that word) I’ve see a lot of stupidity in my 66 years, but nothing even comes close to what’s happening now. I fell helpless in a way I’ve never felt before.
Just the sheer inconsistency of the lockdown regulations drives me nuts. No water on the golf courses, fortunately here in New England it’s not hot anymore, no ball washers (why?) no rakes in the sand traps, it’s all so stupid, even if Corona Chan was as deadly as projected- but as is increasingly clear, it’s not. I also have little hope anything will change if Trump gets reelected. We’re doomed!
Sorry for all the typos. I was MAD!
The letter of the Belgian doctors is exceptionally well organized and a persuasively written account of the Covid-19 debacle. For those of us who would like to educate or respond to others around us concerning the folly of continued lockdowns, a printed copy of this at hand would be very useful. The contentiousness that has grown a health care issue into a political battle is deplorable. By the observations of the Belgian doctors we can see that it’s not just a Republican/Democrat issue, but an issue of the rash and even hubristic wielding of power by almost anyone and everyone holding executive governmental positions world-wide.