I love the strategy employed in these vaccines. It's not a Salk-type model. As I have come to understand it, we're introducing an antagonist to the protein this virus and really all SARS viruses, use to attach themselves to our cells. Once you have both doses your cells are protected from it latching on. Prevents the illness associated with it. Keeps us from having to have a different vaccine for each variant that comes out, like we have with flu.
We achieve herd immunity via exposure, which this does not prevent at all. We build antibodies to the virus the natural way. Which means, yes we can still catch carry and spread this virus, at least until it dies in our system. Can't reproduce or even incubate if it can't latch onto our cells. This is also the reason we were able to produce this in record time vs. the Salk way. It's genius.
The Salk model was to make the vaccine out of samples of the dead virus. This was a breakthrough, previously all we had was giving you the live virus in a small dose, so you would then build up immunity to it without actually catching the disease. (Hopefully) Salk's method ensured you could not get the disease period, once you built up immunity. But his method was tricky, and took months to make and years to test.
This stuff today - we found a protein the virus uses to infiltrate our cells and incubate and multiply. Once this happens the virus makes us sick and can kill. We introduce an antagonist to that protein and make your body produce it, so that if you catch this virus it can't do much except eventually die. But while the virus is in us we have time to develop antibodies to the virus naturally and without getting sick, and become immune. So that if it gets in our bloodstream again it just gets killed outright by our immune system. Accomplishing the same thing Salk did, but without giving us any part of the virus alive or dead.
It's just a pharmaceutical we can quickly and inexpensively mass produce instead of incubating and growing a virus in eggs, killing it then injecting people with it. That takes way too long and is way too costly and there's way too much margin for error. Literally millions have tied testing Salk-type vaccines, and in fact it was a Salk-type vaccine test that gave us the AIDS virus.