Needlestick safety device. Scanning electron micrograph (SEM) of a needlestick prevention device. Every year employees in the health care sector all over the world suffer approximately two million needlestick injuries with the risk of hepatitis and HI virus infection. This small metal sheath is depressed when injecting and then recovers the needle tip when not in use preventing accidental injection. Magnification: x10 when printed 10 centimetres high.