A newborn is delivered to a mother whose hepatitis B surface antigen (HBsAg) status is positive. The nurse is preparing the infant's initial immunization plan. Which of the following statements best explains why both the hepatitis B vaccine AND hepatitis B immune globulin (HBIG) must be given within 12 hours of birth?
- The vaccine alone provides immediate active immunity that is sufficient to protect the newborn from vertical transmission.
- The HBIG provides immediate passive immunity while the vaccine stimulates the infant's own active immune response, together reducing transmission risk.
- The hepatitis B vaccine is given to the mother, while the HBIG is the only agent administered to the newborn.
- Both injections are given together because they contain the same antibodies and the double dose ensures full coverage.