http://www.sciencemag.org/news/2021/08/having-sars-cov-2-once-confers-much-greater-immunity-vaccine-no-infection-parties

The natural immune protection that develops after a SARS-COV-2 infection offers considerably more of a shield against the Delta variant of the pandemic coronavirus than two doses of the Pfizer-BioNTech vaccine, according to a large Israeli study that some scientists wish came with a “Don’t try this at home” label. The newly released data shows that people who once had a SARS-COV-2 infection were much less likely than vaccinated people to get Delta, develop symptoms from it, or become hospitalized with serious COVID-19.

The study demonstrates the power of the human immune system, but infectious disease experts emphasized that this vaccine and others for COVID-19 nonetheless remain highly protective against severe disease and death. And they caution that intentional infection among unvaccinated people would be extremely risky. “What we don’t want people to say is: `All right, I should go out and get infected, I should have an infection party.’” says Michel Nussenzweig, an immunologist at Rockefeller University who researches the immune response to SARS-COV-2 and was not involved in the study. “Because somebody could die.”