Lysine is effective because it acts against Influenza A, which is what SARS-2 C-19 really is. There is no documented Corona Virus 19 as yet.
Lysine inhibits Influenza A
LINK
https://pubmed.ncbi.nlm.nih.gov/19276537/
That study involves a nutrient mixture (NM) that contains lysine - but also contains Vitamin C, green tea extract and NAC (and other substances), all of which have (in other articles posted here on FR and elsewhere on the internet) been shown to be somewhat effective in helping the body to fight off ALL viruses. So, while I don’t doubt the effectiveness of Lysine (and will likely order some), it isn’t just the Lysine that’s effective. Other nutrients are needed.
From the link you provided:
“A unique nutrient mixture (NM), containing lysine, proline, ascorbic acid, green tea extract, N-acetyl cysteine and selenium among other micro nutrients, has been shown to exert a wide range of biochemical and pharmacological effects....”