Seasonal influenza vaccine (A/New York/39/2012) effectiveness against influenza A virus of health care workers in a long term care facility attached with the hospital, Japan, 2014/15: A cohort study.

The 2014/15 influenza season started earlier than usual, and intense activity was reflection of circulation of antigenically-drifted and vaccine-mismatched dominant A(H3N2) viruses. Although inpatients and health-care workers (HCWs) had a high influenza vaccination coverage rate well prior to the beginning of influenza season, numerous outbreaks of influenza A(H3N2) infection with fatal cases were reported in long-term care facilities (LTCFs) in Japan during 2014/15 influenza season. In January 2015, we were given opportunity to conduct outbreak investigation of influenza A at facility A (LTCF attached with hospital) in Western part of Japan.