ROSH Gastrointestinal Practice Exam 2026 - Free Gastrointestinal Practice Questions and Study Guide

The combination of serologic markers indicating immunity due to vaccination is characterized by the presence of anti-HBs (antibody to hepatitis B surface antigen) and the absence of HBsAg (hepatitis B surface antigen) and anti-HBc (antibody to hepatitis B core antigen). When a person has been vaccinated against hepatitis B, they develop specific antibodies to the surface antigen (anti-HBs), which signifies that the immune system has responded to the vaccine.

In this correct scenario, the presence of anti-HBs suggests effective immunization, while the lack of HBsAg means there is no active infection. The absence of anti-HBc indicates that there has been no past or present infection, confirming that the immunity observed is entirely due to vaccination. This distinct pattern sets apart vaccinated individuals from those who have had a natural infection, which would show a positive anti-HBc.

Understanding these markers is crucial for interpreting hepatitis B serology, especially in distinguishing between post-vaccination immunity and past or current infections.