Synthetic vaccine for Hepatitis B prevention.

• A. Diazepam
• B. Calcium chloride
• C. Sodium bicarbonate
• D. Hepatitis B vaccine

Answer: (D)

The key idea is how a vaccine works to prevent infection. The Hepatitis B vaccine is a recombinant, subunit vaccine that uses a harmless piece of the virus—the hepatitis B surface antigen—to train the immune system. By presenting this antigen, the body mounts an immune response and develops antibodies and memory cells so it can rapidly fight Hepatitis B if exposed in the future. This is active immunization that builds lasting protection, not immediate antibodies supplied from someone else.

This vaccine is designed specifically for Hepatitis B prevention and is produced without using live virus, using biotechnology to generate the surface antigen in the lab. The other options aren’t vaccines: diazepam is a sedative/anticonvulsant, while calcium chloride and sodium bicarbonate are electrolytes and buffering agents used for other medical purposes.