I had been warned before my first Shingrix shot, that the Shingrix vaccine might come with some nasty, but reasonably brief, symptoms post vaccination. I found that I can certainly concur with that warning. Sounds like you had an experience very like mine. But by the third day I was pretty well back to normal. But not nearly as alarming as my small pox vaccination I had in 2001 after 9/11.

Smallpox? Because they thought that could be used as a terrorist bioweapon?

Yes, because of the concern about the anthrax spores after 9/11. They needed a volunteer who would see potential small pox patients, and I knew I had been vaccinated twice as child. And then once again in 2001. I had a mild fefer, and a distinct viral prodrome - aching, felt sick, tired, yucky. But after 36-48 hours it left and I was fine, as I expected, but wondered a bit about it, for several hours.

Taught me to be more careful when I choose to volunteer 😇 Still, I would do it again, under similar circumstances.