Did they give you the Viralys gel or powder? Viralys is basically l-lysine, an amino acid that interferes with arginine absorption. Arginine (another amino acid) is needed for the herpes virus to replicate. Since lysine is an arginine antagonist, symptoms of the herpes virus should diminish while taking it.
You can get just straight up l-lysine powder from a drug store or health food store, probably for cheaper than what's available at the vet. I'm not a fan of the Viralys gel, which contains yucky ingredients like sodium benzoate, maple flavour (????) and artificial sweetener. The powder is a better choice, but in that case you might as well save some bucks and go to the store.
What are you feeding your kitty? The best way to boost a cat's immune system is with a quality protein, low carb wet food.
ETA - Ah-ha, I'm a slow typer today.
"To close your eyes will not ease another's pain." ~ Chinese Proverb
“We must not refuse to see with our eyes what they must endure with their bodies.” ~ Gretchen Wyler