I think that for the question to be useful, everyone needs to remember that at this point vaccines are thought to be as effective as advertised only for about 3 months. After that? We do not know because we are, effectively, in the phase 3 mass trial now. Usually Phase 3 is completed with very large "representative populations" prior to release to the general public, but we rushed to mass vaccination because of the desperateness of the situation.
But if, like me, you are being vaccinated now (I'm in a priority group), it would be an error to think that, for example, you are "good to go" for volunteering to be in close quarters with dozens and dozens of different people on successive days for 2-4 weeks after Spain re-opens to outside EU visitors at the end of August or early September.
We will know far far better by the end of 2021 whether the vaccines are stable for protection over time, and useful against variants.
The two significant risks right now are 1) that rolling vaccination priority groups place phase 1 recipients in expired protection status before we finish the final rounds of delivery, and 2) that the current vaccines cannot quell the pandemic because the roll-out is too slow (allowing people to start running around as though they are "good to go" when the data show that they are not, and allowing mutations time to take hold).
Really people... love the camino from afar. Send your money to the businesses individually, to the charities distributing funds to albergues, and buy their remote offerings (maps, books, Ivar's store...), but if we really love the people of Spain and not just our privilege to stomp all over their country, then I think we should leave Camino to the Schengen approved "locals" for 2021.