Apple is updating the syringe emoji because of the Covid vaccine.
Instead of the syringe being filled with blood, now it's filled with a clear blue liquid.
According to Emojipedia, there is a consistent demand for an emoji to represent the one hope out of the pandemic of the past year: vaccination.
A good emoji can stand in for multiple purposes, and the issue with showing blood in the syringe emoji is the unnecessary limitation. Removing the specific liquid inside allows for versatility.