According to a letter by Dr Mark Hobart to Brett Sutton, if you "vaccinate" people who have previously had Covid-19 illness there is up to 112% increase of requiring hospitalization due to severe adverse reactions, which is especially dangerous in the elderly.
https://www.covidmedicalnetwork.com/open-letters/Mark-Hobarts-Letter-to-Sutton.pdf
Mark cites the study found, https://www.mdpi.com/2075-1729/11/3/249/htm
I wrote to the Covid Medical Network https://covidmedicalnetwork.com/ requesting all the studies relating to natural immunity and covid19 and they sent me, 141 studies relating to natural immunity.

And the following links
https://m.theepochtimes.com/mkt_morningbrief/naturally-immune-people-at-little-risk-of-reinfection-severe-disease-from-covid-19-study_4126747.html?utm_source=morningbriefnoe&utm_medium=email2&utm_campaign=mb-2021-11-28&mktids=0449f116506200f5b2546d0231069968&est=wja4is0CbFTALQqhvCoMdZovykO2RHy3TBb1dBti3lRyN7SJzrNMzvgZd10%3D
https://rumble.com/vq1n1i-natural-immunity-is-robust-complete-and-durable.html
worldcouncilforhealth.org/resources/natural-immunity-vs-vaccine
https://drtrozzi.org/2021/11/16/natural-immunity-beats-vaccine-by-27-times/
https://m.theepochtimes.com/suspended-medical-ethics-professor-aaron-kheriaty-on-vaccine-coercion-risks-and-natural-immunity-part-1_4077433.html
https://www.theepochtimes.com/mkt_morningbrief/ample-scientific-data-congresswoman-introduces-natural-immunity-is-real-act_4066937.html?utm_source=morningbriefnoe&utm_medium=email&utm_campaign=mb-2021-10-27&mktids=8cbfd2f506c65b5b64a26e4d3a891200&est=qjaazSyBXyaSVsT%2BFghc4PndjrJA62HRWhI8nZUkQcM%2FkdoUETlL5EBGFdgX3dhLeQ%3D%3D
https://aaronsiri.substack.com/p/the-obvious-wins-again-natural-immunity

I think we can safely conclude as Dr Peter McCullough states that natural immunity is robust, complete and durable.
Geert Vanden Bossche has repeatedly stated that one cannot "vaccinate" ones way out of a pandemic with a leaky, non sterilizing vaccines and to let the young and healthy acquire natural immunity to end the pandemic.