Typical preparations, most especially those sold for vaping, turn out on examination to have ~2% of the amount of CBD advertised, where they have any. I.e., they have just enough that a crude test of presence shows something present.

That said, I buy from a premium dispensary and I have no idea what's vended in smoke shops.

I read one good-quality paper that reported an effect, and suggested plausible mechanisms. But the authors cautioned it needed more work before it could be recommended clinically. In particular, there was no hint it might prevent infection, or be useful to treat mild cases. The perhaps surprising bit was that THC interfered with the effect of the CBD.

The US NIH says that fluvoxamine is useful to treat serious cases. Any doctor can prescribe that.