Omicron is very resistant to the antibody response of the vaccines - the antibodies are supposed to cover the protein spikes which latch onto and enable infecti

Omicron is very resistant to the antibody response of the vaccines - the antibodies are supposed to cover the protein spikes which latch onto and enable infection of cells. The t-cell response to infected cells learned from the vaccine, though, is very effective. Which is why vaccinated people still get infected (at a lower rate) but are many times less likely to get very sick, and almost none end up in ICU. The vaccines are effective.