Proof of COVID-19 vaccination when users try to log in to Bitcointalk. I would add new fields under the password where you have to enter the dates you received your vaccines, the manufacturer, and serial codes from the bottles. Whatever you enter would lead to different error messages requiring you to report to your nearest health authority. Those who need help with filling out the fields should click on the help page that shows a photo of a random text in Latin that no one can understand.