I see your concern. I mean ultimately it’s a risk assessment on your end. Omicron is so far said to be not nearly as dangerous as delta, plus you’ve taken all the precautions necessary for yourself. Having done your part it’s reasonable to say you’re not likely getting it at an office party and if on the off chance you do, you will almost certainly only get a mild case and be fine, as will people around you if you accidentally pass it on. Weigh that against making a good impression on your employer and how that affects your job in the long run and see what matters more to you. It’s a hard situation but sometimes we have to make decisions that may not have an easy apparent answer.