This is from an article published in February 2021. It is a retrospective observational study using the national SARS-CoV-2 infection information from Austria. It involves 2020 data.
The study shows that there was a relatively low re-infection rate of SARS-CoV-2 in Austria. Protection against SARS-CoV-2 after natural infection was comparable with the best estimates of vaccine efficacy.
Keep in mind that this information pertains to the original SARS-CoV-2, before the variants started to appear. Regardless of this, it shows the importance of taking into consideration natural immunity when creating health policies with respect to COVID-19.