Here's an excerpt from a paper published in "Journal of Inflammation Research" by Dove Press for a popular and controversial herbal supplement from India:
Coronil effectively inhibited the interaction of ACE-2 not only with the wild-type S protein (SWT) but also with its currently prevalent and more infectious variant (SD614G) and another mutant (SW436R) with significantly higher affinity toward ACE-2
Now assuming what the paper says is true, the herbal drug is mediating the interaction between spike protien and host cells.
In vaccination, the spike proteins are introduced to body through various methods, so that the immune system can interact with it and familiarize itself with the spike protein before hand.
But if the herbal drug, as claimed, reduces the interaction of spike protein itself, then is it a possibility that the drug can interfere in the efficacy of vaccine?