An unvaccinated healthcare worker sustains a percutaneous exposure to blood from a hepatitis B surface antigen-positive source. Within what window should post-exposure prophylaxis be given?

Correct answer: D. Within 24 hours

• A. A week is the outer boundary beyond which prophylaxis is not recommended, not an equally effective alternative.
• B. Prophylaxis given at 25–48 hours still has value, but this is not the target window and outcomes are worse than immediate administration.
• C. By 49–72 hours efficacy has fallen considerably.
• D. CORRECT. Hepatitis B immune globulin plus the first dose of hepatitis B vaccine should be administered as soon as possible, ideally within 24 hours. Efficacy declines steeply with delay, and prophylaxis is generally considered of little value beyond 7 days for percutaneous exposure.

Note: Practical sequence after any percutaneous exposure: wash the site with soap and water immediately (do not squeeze or use caustics), report it at once, identify and test the source patient, and start PEP within hours. Note that HBV is far more transmissible than HIV or HCV — roughly 30% transmission risk from an HBeAg-positive source versus about 1.8% for HCV and 0.3% for HIV. A fully vaccinated worker with documented anti-HBs above 10 mIU/mL needs no prophylaxis at all.