In yesterday’s General blog post, I pointed to a study from Israel that said that Pfizer was only 64% effective. This thread does a takedown of that study.
This preprint also says that AZ+Pfizer is a lot better (in test tubes, anyway) than AZ+AZ, and even a bit better than Pfizer+Pfizer.
This article reports that they have found a metabolism by-product which correlates with severity of COVID-19 disease, and which is higher in men than women.
This paper looks at which Italian health care professions were most/least at risk from COVID-19: