Question

checkpoint 06
what is a vaccination?
an injection of blood taken from another person who has no bacteria
an injection of a chemical formula that forms a shield around bacteria
an injection of a full - strength form of bacteria that causes a disease
an injection of weakened bacteria that creates immunity to a disease

Explanation:

A vaccination is an injection of weakened bacteria (or antigens) that stimulates the immune system to create immunity against a specific disease. It's not about injecting blood from another person (no bacteria - incorrect as blood has components beyond just absence of bacteria in that context), not a chemical formula shielding bacteria (not the mechanism), and not a full - strength disease - causing bacteria (that would cause the disease, not prevent it).

Answer:

an injection of weakened bacteria that creates immunity to a disease