HBV immune globulin prophylaxis is less effective if treatment is delayed beyond how many hours after birth?

• A. 12 hours
• B. 24 hours
• C. 48 hours
• D. 72 hours

Answer: (C)

Timing is crucial for HBV immune globulin prophylaxis because providing passive antibodies promptly after birth helps neutralize any virus exposure before it can establish infection in the newborn. The protective effect is strongest when HBIG is given as soon as possible, with the practical window up to about 48 hours after birth. If administration is delayed beyond 48 hours, the likelihood of effectively preventing transmission drops significantly, making protection far less reliable. In practice, HBIG is often given within 12 hours along with the hepatitis B vaccine to maximize protection, but the key threshold for reduced effectiveness is 48 hours.