Table 3. Nurses’ risk of acquiring SARS based on use of personal protective equipment^a.

Type of personal protective equipment	Attack rate (%) according to personal protective equipment used		Relative risk (95% CI)	2-Tailed Fisher exact p value
	Consistent	Inconsistent
Gown	3/20 (15)	5/12 (42)	0.36 (0.10 to 1.24)	0.12
Gloves	4/22 (18)	4/10 (40)	0.45 (0.14 to 1.46)	0.22
N95 or surgical mask	3/23 (13)	5/9 (56)	0.23 (0.07 to 0.78)	0.02
N95a	2/16 (13)	5/9 (56)	0.22 (0.05 to 0.93)	0.06
Surgical maskb	1/4 (25)	5/9 (56)	0.45 (0.07 to 2.71)	0.56
N95 versus surgical maskc	2/16 (13)	1/4 (25)	0.50 (0.06 to 4.23)	0.51

^aSARS, severe acute respiratory syndrome; CI, confidence interval.
^bThe comparator is use of no mask. The denominator n (total=32) changes for these comparisons as the nurses who consistently used the indicated personal protective equipment were compared to nurses who wore no masks.
^cConsistent use of the N95 mask versus consistent use of a surgical mask. The denominator n (total=32) changes for these comparisons as the nurses who consistently used the indicated personal protective equipment were compared to the indicated unique group, rather than to the rest of the nurses.