Increased risk of SARS-CoV-2 reinfection associated with emergence of Omicron [pdf]
medrxiv.org
medrxiv.org
When you hear that Omicron evades natural immunity be aware that this is the paper driving that quip. If other papers emerge please share!
This BBC report touches on the paper: https://www.bbc.com/news/health-59520945 importantly noting some confounding factors not discussed in the paper.