If we’re still talking about the OP question - Rush isn’t wrong on that.
It’s a simplified way of looking at it but yes, a vaccine is deactivated virus or particular portions of it’s RNA so your body has an immune reaction. Humanity has been doing that since the Middle Ages, it was called variolation when doctors would infect people using either pustules of people dying from smallpox or by getting people cowpox as an inoculation against smallpox.
And he is also right on the flu vaccine, we don’t know what the next strain of the flu will look like so we just kind of guess using last 6 months worth of flu strains. The flu mutates about every 6 months but generally you’re fine if you get every other strain.
The problem with the COVID-19 is that there is no ‘similar enough’ vaccine. The initial SARS outbreak was the only close enough virus and funding into a vaccine for SARS was discontinued by the Federal government in FY2016. Even though funding for NIH has once again grown over the last 2-3 years, you don’t just start up a vaccine study from scratch in 3 months time, we’re talking 5-10 years under a regular funding regime. This could be accelerated somewhat to 1-2 years provided the FDA doesn’t attach a bunch of red tape to the approval process but it’s not “let’s just spin up a vaccine from what we have”