Which statements is/are correct with reference to the animal serum in vaccines?

• A. Horses used to be injected with small doses of bacteria that caused diphtheria so that they could develop antibodies.
• B. The use of horse serum as an antibody supplement in the diphtheria vaccine is more than 100 years old.
• C. None of these
• D. Both A & B

Answer: (D)

The use of horse serum as an antibody supplement in the diphtheria vaccine is more than 100 years old. Horses used to be injected with small doses of bacteria that caused diphtheria so that they could develop antibodies.