Those MIT lectures are not your typical Youtube videos my friend. There's a LOT of great information to be gotten which used to take a college degree to attain.
I brought in Omicron because we were talking about with IT the protection against infection with the current vaccines is SO low, that it does not materially prevent further transmission through the population. Of course it is great possible news that it might be less deadly, but the fact remains that the "knights of morality" out there are insinuating that unless virtually everyone gets vaccinated, this will go on forever and that's just not true.
Now as far as breakthrough infections go: the article states that between April and November there were 1.8 million breakthrough infections. These were POSITIVE TESTS! We know that even with Delta, the vaccine protection against severe disease is quite high, so there HAVE to be many more that WERE positive but did not get tested. I don't think 10 million is unreasonable....