Abstract
BackgroundIn 2016/17, seasonal influenza vaccine was less effective in those aged 65 years and older in the United Kingdom. We describe the uptake, influenza-associated mortality and adjusted vaccine effectiveness (aVE) in this age group over influenza seasons 2010/11–2016/17. Methods: Vaccine uptake in 2016/17 and five previous seasons were measured using a sentinel general practitioners cohort in England; the test-negative case-control design was used to estimate pooled aVE by subtype and age group against laboratory-confirmed influenza in primary care from 2010–2017. Results: Vaccine uptake was 64% in 65–69-year-olds, 74% in 70–74-year-olds and 80% in those aged 75 and older. Overall aVE was 32.5% (95% CI: 11.6 to 48.5); aVE by sub-type was 60.8% (95% CI: 33.9 to 76.7) and 50.0% (95% CI: 21.6 to 68.1) against influenza A(H1N1)pdm09 and influenza B, respectively, but only 5.6% (95% CI: - 39.2 to 35.9) against A(H3N2). Against all laboratory-confirmed influenza aVE was 45.2% (95% CI: 25.1 to 60.0) in 65–74 year olds; - 26.2% (95% CI: - 149.3 to 36.0) in 75–84 year olds and - 3.2% (95% CI: - 237.8 to 68.5) in those aged 85 years and older. Influenza-attributable mortality was highest in seasons dominated by A(H3N2). Conclusions: Vaccine uptake with non-adjuvanted, normal-dose vaccines remained high, with evidence of effectiveness against influenza A(H1N1)pdm09 and B, though poor against A(H3N2), particularly in those aged 75 years and older. Forthcoming availability of newly licensed vaccines with wider use of antivirals can potentially further improve prevention and control of influenza in this group.
Highlights
The United Kingdom (UK), like many other countries in Europe, North America and Australasia, has a longstanding inactivated influenza vaccine programme including for all those over 65 years of age
During influenza season 2016/17, among 65–69-yearolds in England, influenza vaccine uptake was 64% (55,818/87,566) compared with 74% (52,873/71,298) in 70–74 year olds and 80% (71,072/89,228) for those aged between 75–84 years or aged 85 years and older (28,143/35,097)
During influenza seasons 2011/12–2016/17 in England, influenza-associated mortality estimates were higher in both the 65–74-year-olds and those aged 75 years and older during influenza A(H3N2) compared with A(H1N1)pdm09 dominated seasons (Table 2)
Summary
The United Kingdom (UK), like many other countries in Europe, North America and Australasia, has a longstanding inactivated influenza vaccine programme including for all those over 65 years of age. The UK universal influenza vaccine programme for those aged 65 years and older was first started in 2000/01 [1], following several seasons of intense A(H3N2) activity associated with substantial morbidity and excess mortality in this older age group [2]. This together with vaccination effectiveness (VE) estimates at that time [3] informed the decision to offer influenza vaccine free of charge to all individuals aged 65 years and older in addition to high-risk groups, such as those with underlying chronic respiratory and cardiovascular disease. Forthcoming availability of newly licensed vaccines with wider use of antivirals can potentially further improve prevention and control of influenza in this group
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