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

Seasonal influenza is a serious public health problem that can cause severe illness, hospitalisation and death. Influenza vaccination is one of the most effective methods for preventing influenza and its complications. In Hong Kong, people aged 50 to 64 were added as a recommended priority target group for influenza vaccination by the Department of Health starting from 2011/12. The coverage rate of the influenza vaccine for this age group was 8.5 percent in 2012/13. In order to explore the reasons for the low influenza vaccine coverage rate, a systematic literature review and a case-control study were conducted. The literature review aimed to explore what demographic, social and psychological factors were associated with the uptake of influenza vaccination among adults from 18 to 64 years. The result of the review was used to inform the design of a case-control study, which aimed to determine factors associated with the uptake of influenza vaccination amongst adults aged 50 to 64 years in Hong Kong. The literature review and the case-control study are presented in publication format. The case-control study was conducted using street intercept interviews from 17 July to 15 August 2013. Cases were adults aged 50 to 64 years who received influenza vaccination in 2011/12 or 2012/13, while controls were the same as cases, except they did not receive the vaccine during the same period. Multinomial logistic regression analysis was performed on the data to explore associations between vaccination status and the variables. The study had a total of 604 respondents: 193 cases (vaccinated) and 411 controls (non-vaccinated), with a case-to-control ratio of 1:2.1. The factors which possessed the strongest associations with influenza vaccination were: ‘eligible for free government vaccine’; ‘willing to receive flu vaccination for free’; ‘perceived having severe or moderately symptoms when contracting flu’; and ‘accept advice from health professional’.