I remember when it was a spoon full of sugar.
Of course they don't have to use ink, only the method is used. There is more than one way to be injected, and the method usually dictates the length of time the drug stays in the system, and the way it is treated by the body. Intravenous, when something is injected into the vein, usually goes straight to work. Good for things like insulin, and painkillers, but they also tend to be broken down quickly. Intramuscular is injected into the muscle, and has a slow release, The ingredients of an injection are usually broken down by the liver, so they stay in the body until they reach the liver. subcutaneous or under the skin seems likely to be good for vaccines, because the skin is one of the most likely places for an infection to attack, so the immune system is likely to be biased to it. However the method may not be the trouble. They are experimenting with DNA, but if they get good results it may be another weapon against disease.