How do they know it protects against a “new” strain and what did they know about it back when they were making these vaccines?
Do people still get a flu shot these days?
Sounds like total BS to me.
“How do they know it protects against a new strain....”
Likely through isolating the strain and infecting monkeys. When I volunteered for the Moderna study they explained that one of the tests performed was vaccinating monkeys and then infecting them with the Covid virus. None of the vaccinated monkeys got sick. None.
I imagine the same protocol is being used now for the variants. They can intentionally infect monkeys, they can’t intentionally infect humans.