Factors associated with uptake of influenza vaccine in people aged 50 to 64 years in Hong Kong: a case-control study.

Background: In Hong Kong, people aged 50-64 years were added as a recommended priority group (recommended group) for influenza vaccination by the Department of Health (DH) starting from 2011/12 onwards. The coverage rate of influenza vaccination for this age group was suboptimal at 8.5 % in 2012/13.