According to a update to the security post on AMD’s newsroom section of the AMD website, AMD’s latest processors are not vulnerable for latest Spectre 3a variant revealed by Microsoft and Google Project Zero.
Spectre Next Generation security flaw probably not applicable to AMD’s Zen-based processors
The latest Spectre NG security flaw is not applicable on AMD’s Ryzen and Epyc processors. AMD’s processors were not mentioned in the Spectre NG press release.