Lots of fools are posting their vaccine cards online, just swipe theirs. Fill out the type of vaccine (Moderna or Pfizer for 2 doses, J&J is only one), and the lot number. Moderna is four weeks between doses, Pfizer is three between doses. There is also a return date to fill out on the back that should correlate to four or three weeks out. The nurse fills in the vaccine info but the name and DOB can be in your handwriting. The right most square is where you got it, which could be Walgreens, the name of a hospital the name of a school, the name of a public health department, you name it. There isn't anywhere on the card that needs to be signed by a health care professional. It's not unreasonable to have both doses in the same handwriting if you "went" to a place with fewer staff, but I would switch it up or even use a different color pen. Stickers have kind of gone by the wayside.

Some states, MI for sure, submit paperwork to their public health department, so if anyone wanted to look you up in MICR you wouldn't show. Be aware of that. There is more documentation than just the card.