A recent study from Israel said that natural immunity is an order of magnitude better than vaccine-induced immunity against delta variant. I don't know who to believe, but if that's the case, then the narrative of "well they should get vaccinated anyway" is really freaking suspicious. We need deeper research on this, and the fact that they haven't researched this is truly scary.
Same study came to the result that getting a shot after surviving an infection (unvaccinated) gives even better protection. The real interesting comparison would be immunity after getting a breakthrough infection compared to other kinds of acquired immunity. I'm sure we'll get that study eventually. https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v...
“Individuals who were previously infected with SARS-CoV-2 seem to gain additional protection from a subsequent single-dose vaccine regimen. Though this finding corresponds to previous reports, we could not demonstrate significance in our cohort.”
At the moment, this does not justify mandating the vaccine for those previously infected.