The thing also with the vaccines and ivermectin possibly causing an issue for big phrama vaccines is that - The COVID-19 vaccines from Pfizer, Moderna and Johnson & Johnson have all received an Emergency Use Authorization (EUA) from the FDA. EUAs may be granted only during a public health emergency *and when there are no adequate, approved, and available alternatives.*

If ivermectin was found to be safe and effective and got FDA approval itself, the vaccines of Pfizer, Moderna and J&J would need to get full approval - meaning longer and more rigorous clinical trial and safety testing. (not that they haven't gone through a certain level of those things, just the bar is set lower with EUAs)

p.s. Sounds like you talked to your doctor about supplementing VitD - but you're mistaken to say there aren't any downsides (especially for regular high doses of D) --- It can cause hypervitaminosis D which in turn causes hypercalcemia (a buildup of calcium in your blood). Just saying as it may be worth double checking :)