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 particularly 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.
Following this change in vaccine policy, influenza vaccine uptake for those aged 65 years and older has increased, reaching a high point in excess of the World Health Organization (WHO) and European Council recommendation of 75% in 2005/06 in England. Although there has been a gradual decline in uptake since that time, coverage was still 70.5% in 2016/17, ranging from 66.6% to 74.5% in other UK countries [4]. Although excess influenza-associated mortality has reduced since the high levels observed during the 1990s, there is still a substantial disease burden on the population, particularly in those aged 65 years and older and most often during seasons with intense influenza A(H3N2) activity [5]. A recently published UK VE study for the 2016/17 season, when influenza A(H3N2) was again the dominant circulating strain, found moderate to good VE in children and younger adults but no evidence of effectiveness in those aged 65 years and older [6]. Newer vaccines that provide direct protection against influenza e.g. adjuvanted, higher dose, cell-based or are recombinant [7] are becoming increasingly available. These, in combination with indirect protection from the progressive rollout of the UK childhood influenza vaccine programme, means that the potential role of these alternative interventions in reducing disease burden in this age group needs to be further explored [7].
The aim of this study was to further describe the recent uptake of influenza vaccine in those aged 65 years and older (including prior vaccine history) to measure influenza-associated mortality in this age group and to estimate the effectiveness of influenza vaccine over the period 2010–2017. The results will help inform optimal approaches to further mitigate the impact of influenza in this enlarging group.