Independently, we found no re-infection among those with prior COVID-19, contributing to 74,557 re-infection-free person-days, adding to the evidence base for the robustness of naturally acquired immunity.

“COVID-19 SARS-CoV-2 preprints from medRxiv and bioRxiv”

https://www.medrxiv.org/content/10.1101/2021.11.15.21265753v1