Do you need to aspirate subcutaneous in vaccine?

Aspiration is generally recommended before injecting a vaccine subcutaneously to reduce the risk of injecting into a blood vessel. By pulling back slightly on the syringe plunger before fully injecting the vaccine, you can check if any blood is drawn into the syringe. If blood is present, you should either reposition the needle and aspirate again, or discard the syringe and use a new one to avoid injecting the vaccine into a blood vessel.