Scientists will be closely watching whether cases caused by Omicron reported on public databases start to supplant those caused by Delta. That could take three to six weeks, depending on how fast the variant moves, experts said.

from Times of India https://timesofindia.indiatimes.com/home/science/covid-19-how-fast-does-it-spread-scientists-ask-whether-omicron-can-outrun-delta/articleshow/87995915.cms