Evaluation of depth and thickness in skin, subcutaneous and muscle tissue at vaccination sites in Japanese infants - Evaluation of depth and thickness in skin, subcutaneous and muscle tissue at vaccination sites in Japanese infants

The thickness of the epidermis was 1.44 - 1.54 mm (95% CI), and the lengths from the skin surface to the muscle fascia and bone were 11.52 - 12.28 mm (95% CI), and 25.66 - 26.93 mm (95% CI), respectively, at the anterolateral thigh. At the center of the deltoid muscle, skin thickness was similar to that at the thigh, furthermore the lengths from the skin surface to the muscle fascia and bone were 8.49 - 9.10 mm (95% CI), and 17.38 - 18.31 mm (95% CI), respectively. The lengths from the skin surface to the muscle fascia and bone were 1 - 2 mm shorter in 2-month-old infants than those in older generations. Therefore, the appropriate needle length for intramuscular injections in Japanese infants was 16 mm (5/8 inch) at any age and sites, and with 25 mm (1 inch) needles at a 90-degree angle being associated with the risk of over-penetration.