UKMLA PLAB AMC USMLE Prometric MCQ

Correct Answer: A

Explanation:
Active immunization has become possible with the advent of hepatitis B vaccine. The original vaccine was prepared from the plasma of hepatitis B carriers. Although this vaccine underwent multistep inactivation that destroyed the infectivity of all known viruses (including HIV), concerns over the origin of the vaccine from high-risk persons limited its acceptance. In 1987, a recombinant vaccine became available, derived from recombinant yeast into which the gene for surface antigen had been inserted. Such vaccines have replaced plasma-derived vaccines.