Omicron Variant report from UKHSA [pdf]

If Omicron continues to grow at the present rate, Omicron case numbers are projected to reach parity with Delta cases in mid- December (this was dated 10th Dec).

Vaccination is less effective against Omicron than against Delta. But shortly after a booster dose, there is about 70% effectiveness.

I haven't got on to anything about hospitalisation rates vs Delta yet; it may still be early days for that.

"To date, there are no cases of Omicron which are reported as having been hospitalised or died through routine reporting. As a result, it is not possible to compare the risk of hospitalisation or death with other variants. However, it should be noted that most of the cases have a specimen date that is very recent and that there is a lag between onset of infection and hospitalisation and death. Future updates will assess severe outcomes from Omicron cases against Delta cases from the same time period."