This is an interesting story from Reuters today: Omicron virus holds cells more tightly, withstands some antibodies, or even appears to shake some of them off. Booster shots seem to increase antibodies, which is crucial in how much human defences improve in fighting it. 

Omicron thrives in airways, not lungs; new data on asymptomatic cases | Reuters:

Compared to the earlier Delta variant, Omicron multiplies itself 70 times more quickly in tissues that line airway passages, which may facilitate person-to-person spread, they said. But in lung tissues, Omicron replicates ten times more slowly than the original version of the coronavirus, which might contribute to less-severe illness.

…Chan added, “By infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic. Therefore, taken together with our recent studies showing that the Omicron variant can partially escape immunity from vaccines and past infection, the overall threat from Omicron variant is likely to be very significant.”