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

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

A. The use of horse serum as an antibody supplement in diphtheria vaccine is more than 100 years old.

B. Horses used to be injected with small doses of bacteria that caused diphtheria so that they could develop antibodies.

C. Both A & B

D. None of these

Explanation:

The Central Government of India recently issued a clarification stating that Covaxin, the Covid-19 vaccine developed by Hyderabad-based Bharat Biotech, did not contain the serum of a newborn calf.  Historically, animal serum has been used in the development of vaccines in other ways as well. The use of horse serum as an antibody supplement in 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.