McCullough’s qualifications are impressive and sound, I will take his concerns over any “fact checker” with an obvious agenda. There’s at least some evidence out there for this shedding, it’s moved beyond being theoretical at this point. And I’ve seen other qualified researchers say things similar to McCullough. The risk is probably small overall without an exchange of bodily fluids, but some evidence suggests even that isn’t necessary. It would be funny if the anti-vaxxers now start shunning the vaxxed the way the vaxxed once shunned them lol.
Here’s an article on this subject with links to the study McCullough is referring to: