I got my first dose of the Moderna vaccine a week ago, and started designing this while I rested afterwards.
There are two versions of this: a 20mm small, earring-sized version, and a larger version with a bit more detail. I wanted the 'liquid' area to be easy to dab a bit of paint or nail polish into, so they have a walled-off recess. (I would love to see a dual extrusion of this also!)
I posted more variations on the design here including one without a heart shape and ones that are better for making into pins.
It's designed to be printed at 0.2mm layer height, 0.4 nozzle width; if you want to print it finer, it would be easiest to try 0.1mm height instead. (The model layers are multiples of 0.2mm in height, and horizontal details are generally at least a tiny bit bigger than 0.4mm to help slicers cooperate.)
You can hang these from either loop in the heart; the one directly above is slightly thicker and thus sturdier and will hang roughly perpendicular; the bigger loop will make it hang more diagonal.
I would love to see any prints you make!
Note: I have no idea if this works with resin printing, but I would also love to see if you try that or adapt the design.