There's a related topic never discussed, which I would say is simpler and even more fundamental that the one involving exosomes. That question is: "Are viruses alive?"

If they are not some type living creature, that puts a stake through the heart of pretty much everything conventional science has to say about viruses, and particularly about vaccines. That's why it's never discussed. It's the old, "Spot me one miracle and I can prove the rest."

Anyone interested can investigate the issue for themselves, but I suspect you'll find it like walking into a fog bank. It looked solid from the outside so you always assumed it was, but when you get in there you find it extremely tenuous and there's nothing at all to grab on to.