Omicron is extremely transmissible. If anyone in a moderately-sized social gathering indoors (e.g., ten people meeting up in a house for Christmas dinner) has Omicron, most people are likely to become infected, regardless of vaccine status. Omicron also has a wider range of symptoms. It is therefore vital to stay at home if you have symptoms typical of a cold; stay away from anyone who has cold symptoms; take a Lateral Flow Test immediately before mixing, and to ensure all indoor spaces where people are mixing are as well ventilated as possible.
The Planning Template is designed to help people make decisions about whether to defer meeting with friends and family over the coming high-risk winter holiday season. If you decide to meet up, it suggests how best to do this in order to minimise risk to everybody involved.