Incidence of getting Hep B from a contaminated needle?

• A. 1 in 3
• B. 3 in 1000
• C. 1 in 100
• D. 1 in 10

Answer: (A)

Hepatitis B is highly infectious through blood, so a needlestick from an HBV-infected source carries a substantial chance of transmission to someone who is not immune. When the source is actively infectious (HBsAg positive, often with active replication indicated by HBeAg), the risk to an unvaccinated, nonimmune recipient is about one in three. That estimate reflects the high viral load HBV can have in blood and the percutaneous route of exposure. The exact risk varies with how infectious the source is and how well the recipient is immune, but this upper-range figure captures the typical substantial risk scenario. If the person has been vaccinated or has immunity, the likelihood drops dramatically, and post-exposure prophylaxis with the HBV vaccine—and HBIG if indicated—can prevent infection. So the 1 in 3 choice aligns with the high-infectivity risk for HBV after a contaminated needle exposure.