Vaccines
One might think you’d have to have quite a high vax rate before case counts would come down. Israel currently is basically back to normal, and their vax rate is only about 60%.
Want to know more about what scientists think might be behind the AZ clotting issue? The Atlantic has a good article about on the subject.
Here’s a good article on the attempt to make one vaccine to rule them all (well, all the coronaviruses).
There is something called “imprinting” in the immune system, where for some viruses, your first response is kind of a high-water mark for how you respond in the future. I got this metaphor in my head: vaccine #1 teaches you how to use pistols against Bad Virus; when vaccine #2 shows up with a bazooka, the immune system says, “never mind, we got this, we know how to handle Bad Virus” and sends the bazooka away. Here’s the article I read on imprinting, see if you think I got it right.
Add yet another condition to the set of conditions which are known to impede people from good immune responses, and which (surprise!) impede COVID-19 vaccination responses to the first dose, but the second dose seems to give a good enough response. In addition to pregnancy, lactation, kidney failure, and certain types of cancer, now add lymphocytic leukemia and multiple myeloma.