A 28-year-old male medical resident is evaluated in the occupational health clinic immedia… — USMLE Step 2 CK

A $28$ -year-old male medical resident is evaluated in the occupational health clinic immediately after sustaining a needlestick injury with a hollow-bore needle. The needle was just used to draw blood from a patient. The source patient is known to be positive for hepatitis B surface antigen (HBsAg) and negative for both HIV and hepatitis C virus. The resident is asymptomatic. A review of his employee health records indicates that he completed the standard hepatitis B vaccination series $4$ years ago. Blood is drawn from the resident, and laboratory studies show the following:

Hepatitis B surface antigen (HBsAg): Negative
Hepatitis B surface antibody (Anti-HBs): Positive ( $150 \text{ mIU/mL}$ )
Hepatitis B core antibody (Anti-HBc): Negative

Which of the following is the most appropriate next step in management?

A
Administer a hepatitis B vaccine booster only
B
Administer hepatitis B immunoglobulin only
Provide reassurance and no further interventionAnswer
D
Administer both hepatitis B immunoglobulin and a vaccine booster
E
Initiate prophylactic therapy with tenofovir

Answer

Provide reassurance and no further intervention

The correct management is to provide reassurance and no further intervention. This patient has been previously vaccinated against Hepatitis B and currently has an isolated positive Hepatitis B surface antibody (Anti-HBs) titer of

150 \text{ mIU/mL}

. A titer of

10 \text{ mIU/mL}

or greater indicates adequate, long-term protective immunity. According to current occupational health guidelines, healthcare workers who have been fully vaccinated and have a documented protective antibody response do not require post-exposure prophylaxis (PEP) after an exposure to Hepatitis B, even if the source patient is definitively known to be HBsAg-positive. The worker's memory B cells will rapidly mount an appropriate immune response to neutralize any introduced virus.

Step-by-Step Solution

Evaluate the patient's exposure risk.

The patient suffered a hollow-bore needlestick injury from a known HBsAg-positive source, representing a high-risk exposure for Hepatitis B.

Determining the severity of the exposure dictates whether post-exposure prophylaxis might be necessary.

Assess the healthcare worker's baseline immune status.

The patient's laboratory results show a positive Anti-HBs titer of

150 \text{ mIU/mL}

, which is well above the protective threshold of

10 \text{ mIU/mL}

. Negative HBsAg and Anti-HBc confirm this immunity is from vaccination, not natural infection.

Prophylaxis algorithms depend heavily on the exposed individual's pre-existing immunity to the virus.

Determine the appropriate post-exposure prophylaxis based on the immune status.

Because the patient is a documented vaccine responder with an adequate and highly protective titer, no further action is required.

Current guidelines explicitly state that vaccinated individuals with an Anti-HBs titer of

10 \text{ mIU/mL}

or greater require no intervention following an exposure, regardless of the source patient's HBsAg status.

Key Concept

Hepatitis B post-exposure prophylaxis in vaccinated healthcare workers

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