For intramuscular immunizations in infants, which muscle is preferred?

• A. Deltoid
• B. Vastus lateralis
• C. Gluteus maximus
• D. Rectus femoris

Answer: (B)

Infants need an IM injection site that has good muscle mass, is easy to locate, and avoids major nerves and vessels. The vastus lateralis on the anterolateral thigh fits best. It typically has reliable muscle for absorption in babies, is straightforward to locate, and sits away from the sciatic nerve and other key structures found deeper in the gluteal region or near the femur. The deltoid isn’t well developed in infants, making injections harder to place safely there. The gluteus maximus area can risk sciatic nerve injury and is less accessible in small children. The rectus femoris is not favored due to its position and proximity to important neurovascular structures. So, the vastus lateralis is the preferred site for intramuscular vaccines in infancy.