Can you be terminated for not vaccinating? Yes but...

The short answer is not immediately. The median answer is probably but not because you didn't vaccinate yet.  In OHS terms if you replace Vaccinate with Ventilation it might make more sense. Mitigating risk is synonymous with identifying hazards and implementing measures. You always want to eliminate a hazard. If COVID were an atmospheric hazard we would look to ways to eliminate the source. Government OHS may just force businesses to do through the back door what the guise of medical choice can not. This is assuming the hazard to the person is not greater.