The risk profile of Ivermectin is very, very well known, many billions of doses have been used over 40 or so years, the risk profile looks similar to that of aspirin or Tylenol. This vs. an experimental EUA mRNA therapy that has little history of good results with low side effects. Arguably the biggest experiment in the history of medicine.
But if you are the VA, how are you going to make sure your employees are actually, daily taking the ivermectin you have mandated, as an anti-covid prophylactic?