In conclusion, our data indicated changes in cellular profi les during pandemic (H1N1) 2009 virus infection; showed that transient production of IL-6, IFN-γ, and IL-10 are main effectors of the early innate immune response against pandemic (H1N1) 2009 virus; and indicated that adaptive immune responses are impaired in the initial phase after infection. These factors may help clarify the pathogenesis of pandemic (H1N1) 2009 virus and provide new approaches in overcoming severe infections. Pandemic (H1N1) 2009 Risk for Frontline Health Care Workers To determine whether frontline health care workers (HCWs) are at greater risk for contracting pandemic (H1N1) 2009 than nonclinical staff, we conducted a study of 231 HCWs and 215 controls. Overall, 79 (17.7%) of 446 had a positive antibody titer by hemagglutination inhibition, with 46 (19.9%) of 231 HCWs and 33 (15.3%) of 215 controls positive (OR 1.37, 95% confidence interval 0.84–2.22). Of 87 participants who provided a second serum sample, 1 showed a 4-fold rise in antibody titer; of 45 patients who had a nose swab sample taken during a respiratory illness, 7 had positive results. Higher numbers of children in a participant’s family and working in an intensive care unit were risk factors for infection; increasing age, working at hospital 2, and wearing gloves were protective factors. This highly exposed group of frontline HCWs was no more likely to contract pandemic (H1N1) 2009 influenza infection than nonclinical staff, which suggests that personal protective measures were adequate in preventing transmission. A ustralia was affected early in the (H1N1) 2009 infl uenza pandemic with 37,636 cases and 191 deaths reported. The state of Victoria was the fi rst to observe a substantial peak in the number of persons infected (1) . The pandemic was managed within the framework of the Australian Health Management Plan for Pandemic Infl uenza (2) . Guidelines for use of personal protective equipment (PPE) were established in the Victorian Health Management Plan for Pandemic Infl uenza (3) . Recommendations included use of N95 masks, gloves, protective eyewear, and longsleeved gowns.