> MABs not working on Omicron was new to me. Is that based on the vaccine's (in)efficacy against it?

To answer my own question, no:

> But a slew of publications posted on preprint servers report laboratory evidence that Omicron is totally or partially resistant to all currently available treatments based on these monoclonal antibodies.

https://www.nature.com/articles/d41586-021-03829-0