[l33tman]

But won't the mucosa learn to produce the IgA antibodies when you get exposed the next time though? The virus is going to be endemic forever, all who got and will get the vaccine are going to get exposed again and again.

In other words, for the already vaccinated (or post-infected) won't repeated exposure also act as a booster?

[superkuh]

Sure. But that means you're spreading the virus, you're taking a small serious health risk, and you're giving the virus tissues in which it can fall back to while simultaneously mutating under IgG antibody pressure in the lower lungs. That keeps the pandemic going.