Objectives: To identify health care workers most at risk for H1N1 infection before vaccination and compare health outcomes after vaccination.

Methods: The indices used to gauge employee health were laboratory-confirmed H1N1 data, laboratory-confirmed influenza A data, and employee sick hours records. In phase 1 of this 2-phase study, absenteeism records for 6,093 hospital employees before vaccine administration were analyzed according to department and employee position during the spring 2009 H1N1 pandemic.

Results: Records of 123 confirmed reports of laboratory-confirmed influenza A or novel H1N1 infections in hospital employees were also analyzed. Two thirds of the H1N1 cases occurred during June (infection rates in parentheses): 34 in physicians and medical personnel (6.7%), 36 in nurses and clinical technicians (2.2%), 39 in Administrative & Support Personnel (infection rate = 1.2%), 3 in Social Workers & Counselors (infection rate = 1.0%), 8 in Housekeeping & Food Services (infection rate = 2.7%), and 3 in Security & Transportation (infection rate=3.9%). When analyzed according to department, the adult emergency department (infection rate = 28.8%) and the pediatric emergency department (infection rate = 25.0%) had the highest infection rates per department.

Conclusions: Of the reported cases of H1N1 in health care workers, 49% occurred in a population that constitutes less than 20% of the total population studied. Physicians and medical personnel had a higher infection rate than other employee positions, whereas ED personnel had the highest infection rate.

(Disaster Med Public Health Preparedness. 2010;4:47-54)