Effectiveness of influenza vaccination in working-age adults with diabetes: a population-based cohort study
- 1Department of Public Health Sciences, University of Alberta, Edmonton, Canada
- 2Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- 3Department of Community Health Sciences, University of Manitoba, Winnipeg, Canada
- Correspondence to Dr Jeffrey A Johnson, 2-040G Li Ka Shing Center for Health Research Innovation, 8602 112 Street, Department of Public Health Sciences, University of Alberta, Edmonton, Canada, AB T6G 2E1;
- Received 7 December 2012
- Revised 7 February 2013
- Accepted 2 March 2013
- Published Online First 27 March 2013
Background Guidelines recommend influenza vaccinations in all diabetic adults, but there is limited evidence to support vaccinating working-age adults (<65 years) with diabetes. We examined the effectiveness of influenza vaccine in this subgroup, compared with elderly adults (≥65 years) for whom vaccination recommendations are well accepted.
Methods We identified all adults with diabetes, along with a sample of age-matched and sex-matched comparison subjects without diabetes, from 2000 to 2008, using administrative data from Manitoba, Canada. With multivariable Poisson regression, we estimated vaccine effectiveness (VE) on influenza-like illnesses (ILIs), pneumonia and influenza (PI) hospitalisations and all-cause (ALL) hospitalisations during periods of known circulating influenza. Analyses were replicated outside of influenza season to rule out residual confounding.
Results We included 543 367 person-years of follow-up, during which 223 920 ILI, 5422 PI and 94 988 ALL occurred. The majority (58%) of adults with diabetes were working age. In this group, influenza vaccination was associated with relative reductions in PI (43%, 95% CI 28% to 54%) and ALL (28%, 95% CI 24% to 32%) but not ILI (−1%, 95% CI −3% to 1%). VE was similar in elderly adults for ALL (33–34%) and PI (45–55%), although not ILI (12–13%). However, similar estimates of effectiveness were also observed for all three groups during non-influenza control periods.
Conclusions Working-age adults with diabetes experience similar benefits from vaccination as elderly adults, supporting current diabetes-specific recommendations. However, these benefits were also manifest outside of influenza season, suggesting residual bias. Vaccination recommendations in all high-risk adults would benefit from randomised trial evidence.
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