Longitudinal seroepidemiologic study of the 2009 pandemic influenza A (H1N1) infection among health care workers in a children's hospital

BMC Infectious Diseases

Table 4 Univariate and multivariate analyses for factors associated with total seroconversion for 2009 pandemic influenza A (H1N1) in 90 unvaccinated healthcare workers at a children' hospital in Taiwan

Characteristics	No. (median/mean)	Crude OR (95% CI)	P value	Adjusted OR (95% CI)	P value
Age per 10 years¹	(29.2/31)	1.45 (0.71-2.93)	0.305
Male sex	18	0.69 (0.14-3.45)	0.654
Baseline anti-H1N1 titer²	(10.0/12.3)	0.36 (0.07-2.01)	0.245
High risk group³	40	3.34 (0.94-11.80)	0.061	6.51 (1.13-37.52)	0.036
Optimal surgical mask usage	75	3.39E8 (0.00-∞)	0.998
Optimal hand hygiene	83	3.00E8 (0.00-∞)	0.999
ILI episode	21	12.19 (3.23-46.04)	< 0.001	9.14 (2.02-41.36)	0.004
Virologically confirmed 2009 H1N1 infection⁴	9	11.41 (2.54-51.32)	0.002	5.99 (0.98-36.48)	0.052

Abbreviations: OR, odds ratio; CI, confidence interval; ILI episode, influenza-like illness episode.
¹ For every 10-year increase in age, for which integer values 0-3 denote ages of 20-30, 30-40, 40-50, and 50-60, respectively.
² Unit increase in baseline titer, for which integer values 0-8 denote titers of < 10, 10, 20, 40, 80, 160, 320, 640, and 1280 or more, respectively.
³ HCWs in direct contact with patients with 2009 pandemic influenza A (H1N1) infection or their respiratory samples were designated high-risk group.
⁴ Virologically confirmed means either viral isolation or real time polymerase chain reaction was positive of 2009 H1N1 influenza virus.