OBJECTIVES : Reducing influenza infection within a hospital is very important for hospital staff and administrators to prevent the spread of this infection among patients and to maintain hospital functioning. A questionnaire study at a university hospital in Japan was performed in order to investigate seasonal influenza infection and vaccination among hospital staff.

METHODS : A questionnaire survey was performed by the distribution to the hospital staff eligible for vaccination for four years, 2014 FY to 2017 FY. The following items were included: the ages of respondents, whether they lived with children aged <15 years, their preseason vaccination status, and their history of seasonal influenza infection. The source of infection for respondents who contracted influenza was also assessed. Data were analyzed for each influenza season.

RESULTS : The hospital is a tertiary referral university hospital with 600 beds. The number of hospital staff was 1850 hospital staffs in average. The vaccination rates and responding rates were 98.6% (1676/1700) and 66.3% (1111/1676) in 2014, 91.9% (1700/1850) and 85.6% (1455/1700) in 2015, 97.5% (1853/1900) and 88.6% (1642/1853) in 2016, and 97.5% (1901/1950) and 87.8% (1683/1901) in 2017. The odds ratio for developing influenza while living with children aged <15 years ranged from 1.65 (95% confidence interval; 0.97-2.83) in 2014 to 2.65 (1.55-4.16) in 2015. The odds ratio for developing influenza after vaccination ranged from 0.72 (0.32-1.61) in 2016 to 1.52 (0.55-4.25) in 2016, with no significant differences among the four influenza seasons investigated. Regarding exposure to the influenza virus, staff’s home was the most frequent site for respondents living with children aged <15 years, and there was more at-home exposure than workplace exposure among employees overall.

CONCLUSIONS : These findings suggest that protection against influenza infection at home is particularly required for hospital employees living with children aged <15 years.