PHDcomics has a great explainer on Covid-19.
Speaking of Covid-19, I just got a third vaccination the other day because I was in the age group of Canadians that had a mixed variety of vaccines and if I want to travel to the USA I need to have two doses of an approved (down there) vaccine. Now I’ve had an AstraZeneca and two Moderna shots. I felt a bit of a headache after the third shot but overall it was less intense than the first two, and also I didn’t preload up on ibuprofen like I did previously.