Measles exposure: within how many days can immunoglobulin be given to prevent or modify disease in a susceptible person?

• A. Three days
• B. Six days
• C. Ten days
• D. Fourteen days

Answer: (B)

Measles post-exposure immunoglobulin is given within six days of exposure to a susceptible person to prevent infection or lessen the severity of illness. The serum provides immediate passive antibodies, helping to neutralize the virus early enough before it fully takes hold. That six-day window is why this option is the best choice. After this period, the chance of preventing disease drops significantly, and the person may still develop measles, often with a typical or more noticeable course. This prophylaxis is especially important for those at higher risk who cannot rely on timely vaccination alone.