A month on from the Omicron variant of Delta being identified by scientists in South Africa, more is known about it but much remains, and is likely to remain, unclear. Immunity from vaccination or previous infection works less well against Omicron. Probably, however, it makes eventual infection milder. More or less certainly, Omicron can transmit faster than Delta. We don't know whether that is just because of immunity-evasion, or it would spread faster anyway in a population new to Covid.