The Omicron variant was discovered less than a month ago. How can scientists create studies so fast? And how accurate can they be? Also how can they distinguish between the natural effects of a variant so mild that very seldom requires hospitalisation and a vaccine protecting people from said hospitalisation?
Also also, supposing that there was enough time and resources to create a serious study in less than a month, I very much doubt that there was time to have it peer-reviewed.