If a patient has positive anti-HBs, what can be inferred?

• A. Immunity from vaccination or past infection
• B. Active infection
• C. Acute liver failure
• D. Chronic infection

Answer: (A)

The main concept is that the hepatitis B surface antibody (anti-HBs) signals immunity to hepatitis B. When anti-HBs is present, it means the person has protective antibodies, either from vaccination or from recovering after a natural infection.

If someone has anti-HBs without signs of ongoing infection, they’re protected. In vaccination, the typical serology shows anti-HBs positive with anti-HBc negative and HBsAg negative. If a person recovered from a past infection, anti-HBs positive along with anti-HBc positive and HBsAg negative indicates immunity after natural exposure.

Active hepatitis B infection would show HBsAg present, not anti-HBs, and chronic infection involves persistent HBsAg as well. Acute liver failure is not determined by anti-HBs status.

So, positive anti-HBs best indicates immunity from vaccination or past infection.