This explanation looks pretty credible, but it will need to be verified by other scholars familiar with medicine and the referenced documents that were said to be copied.
https://arstechnica.com/science/2017/09/the-mysterious-voynich-manuscript-has-finally-been-decoded/

Voymich manuscript
Follow up: the consensus seems to be that the “decryption” is no such thing. See https://arstechnica.com/science/2017/09/experts-are-extremely-dubious-about-the-voynich-solution/