Looking around on social media plus visa agents, there seems to be confusion about how long the health certificate has to be valid for. Some say 6 months.
Health check for work permit. Social media says at least 6 months and others 12.
Visa agents - most say 6 months but I found 2 pretty large companies whom say 12 months.
Any info about this and a link to a government site that confirms it in Vietnamese.