Increasing Influenza Vaccine Uptake. A Comprehensive Approach

General introduction: To prevent influenza virus infection, immunization against influenza has been recommended for individuals with increased risk of complications. These groups comprise individuals of 60 years and older, individuals with risk-elevating co-morbid conditions, residents of nursing homes and other chronic care facilities in The Netherlands and, only recently, health care workers. A reason for suboptimal vaccine uptake in some target groups might be that evidence regarding the clinical benefits of influenza vaccination is conflicting (e.g. in patients with diabetes), that relevant determinants of vaccination behaviour have not been identified adequately (e.g. in smokers or health care workers) or that interventions to invoke a change in behaviour have not been built upon a coherent theoretical base. Clinical effectiveness of influenza vaccination in diabetic patients: We showed that the vaccination was associated with a 56% reduction in any complication (95% confidence interval [95% CI] 36-70%), a 54% reduction in hospitalizations (95% CI 26-71%) and 58% reduction in deaths (95% CI 13-80%). Among study subjects aged 18-64 years reductions in the occurrence of any complication were higher than among those aged over 65 years (72% versus 39%). Behavioural determinants of influenza and pneumococcal vaccination among smokers and non-smokers: We showed that in smokers and non-smokers similar determinants are associated with non-compliance. In addition, we showed that if smokers are considered a high-risk group and therefore targeted for vaccination some important issues need to be taken into account in vaccination programs. Influenza vaccination of health care workers: We developed a multivariate prediction model with 13 determinants to accurately predict influenza vaccine uptake on a HCW level (area under the receiver operating curve [AUC] of 0.95). These determinants were used to apply the intervention mapping method to develop an intervention program to change vaccination behaviour among HCWs in nursing homes. Next, we conducted a cluster randomised controlled trial in 33 Dutch nursing homes to assess the effects of this multi-faceted intervention program on influenza vaccine uptake among HCWs. In the intervention group, influenza vaccine uptake after the program was on average 9% higher than in the control group (relative risk 1.59, 95% confidence interval: 1.08-2.34, p=0.02). In all, 25% of all HCWs in the intervention group were vaccinated against influenza compared with 16% in the control group. Finally, we showed that in 2008 the average influenza vaccine uptake among HCWs in Dutch nursing homes was still only 19 percent and that only a minority of nursing home management (24%) agreed that mandatory vaccination should be implemented if voluntary vaccination fails to reach sufficient vaccine uptake among HCWs. General discussion: To further increase influenza vaccine uptake we encourage that efforts to further increase influenza vaccine uptake among patients with diabetes will be renewed, that healthy smokers will be informed on influenza vaccination and concerning HCWs we recommend improving our intervention program and implementing it nationwide over a longer time period. However, if this does not result in sufficient vaccination rates we advocate the implementation of mandatory influenza vaccination of HCWs in Dutch nursing homes.