This study demonstrated that natural immunity confers longer lasting and stronger
protection against infection, symptomatic disease and hospitalization caused by the
Delta variant of SARS-CoV-2, compared to the BNT162b2 two-dose vaccine-induced
immunity

https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v1.full.pdf




see also
People given both doses of the Pfizer-BioNTech vaccine were almost six-fold more likely to contract a delta infection and seven-fold more likely to have symptomatic disease than those who recovered
. . . This analysis demonstrated that natural immunity affords longer lasting and stronger protection against infection, symptomatic disease and hospitalization due to the delta variant

https://www.bloomberg.com/news/articles/2021-08-27/previous-covid-prevents-delta-infection-better-than-pfizer-shot?utm_source=twitter&cmpid=socialflow-twitter-business&utm_content=business&utm_medium=social&utm_campaign=socialflow-organic