Table 3. Attack rates for healthcare workers (HCWs) with H1N1 influenza infection classified by occupation, work location, and vaccination status.

Variables	Number of participants	Number of infections (%)	OR (95% CI)	p value
Occupation				0.027
Nurse	2032	31 (1.5)	1
Physician	778	8 (1.0)	0.67 (0.31–1.47)	0.316
Other clinical HCW	1176	8 (0.7)	0.44 (0.20–0.97)	0.040
Administrative and ancillary worker	977	4 (0.4)	0.27 (0.09–0.75)	0.013
Working location				<0.001
Wards	1201	25 (2.1)	1
OPD	639	12 (1.9)	0.90 (0.45–1.80)	0.767
ER	172	3 (1.7)	0.84 (0.25–2.80)	0.770
ICU	577	7 (1.2)	0.58 (0.25–1.34)	0.203
Non-patient care locations	2374	4 (0.2)	0.08 (0.03–0.23)	<0.001
Vaccination
Pre-vaccination	4963	47 (0.9)	1	<0.001
Post-vaccination	4740	4 (0.1)	0.09 (0.03–0.25)

ER, emergency room; ICU, intensive care unit; OPD, outpatient department; OR, odds ratio; CI, confidence interval.