It’s the lot number on the vaccine cardAbout a 0% chance as outlined in some states there is zero requirement regarding proof of identity. So even if they had access to every database in the US they would still have holes in their data since the individual could have chosen to without their information or had the vaccination at a non-tracked location.
The lot numbers can be looked up according to location where that lot went and date that lot was used
No match or invalid lot number=false record