Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Figure 42.18 Vaccines are often delivered by injection into the arm. (credit: U. Navy Photographer's Mate Airman Apprentice Christopher D. Blachly).


Question: What preventative measure is often delivered by injection into the arm?
vaccine
Vaccine.