Table 1 Injury rates per worker population with 95% confidence intervals.

Security level	Total staff population	Injuries (n)	Rates of staff injury per 1000 staff	95% CI
Medium security	13 986	7	0.5	0.13–0.87
Maximum security	12 690	7	0.6	0.14–0.96
Mixed security*	11 511	23	2.0	1.18–2.81
Total	38 187	37	1.0	0.66–1.28

*Mixed security prisons had both maximum and medium security units.