Seasonal Influenza Vaccine Effectiveness

Book cover of Seasonal Influenza Vaccine Effectiveness (SIVE): an observational retrospective cohort study – exploitation of a unique community-based national-linked database to determine the effectiveness of the seasonal trivalent influenza vaccine.

Each year, influenza causes substantial morbidity and mortality, particularly in people aged ≥65 years and those with underlying serious comorbidities. In the USA, for example, it has been estimated that influenza is responsible for 186,000 excess hospitalisations and 44,000 excess deaths at a cost of $87B per year. In England, influenza-related mortality is estimated to be as high as 8600 deaths per year. National vaccination strategies represent a potentially important approach to reducing both influenza-related illness and death, hence the considerable investment in this preventative strategy in many parts of the world. In populations at risk of developing influenza-related complications (for example, adults aged ≥65 years and people with medical conditions such as diabetes, heart or respiratory disease or immune deficiency), there is a paucity of reliable estimates of efficacy from randomised controlled trials, which offer the best opportunity to produce unbiased estimates of vaccine effectiveness (VE). This measure is expressed as a percentage, and represents a reduction in risk provided by the vaccine for a given outcome (e.g. laboratory-confirmed influenza). Furthermore, it is thought that influenza vaccine is less effective in the oldest age groups owing to immune senescence.

In the book, the authors aimed to examine the effectiveness of the seasonal influenza vaccination in individuals registered with a national sample of general practices in Scotland. More specifically, our three objectives were to evaluate:

1. uptake of the influenza vaccine by the relevant at-risk populations, i.e. patients with relevant comorbidities and those aged ≥65 years, as well as by the general population
2. the reduction in the expected incidence of influenza-related morbidity and mortality in these at-risk groups, as this is the major rationale behind current immunisation policies
3. the effectiveness of the influenza vaccine in the population as a whole.

To cite the book:
Simpson CR, Lone N, Kavanagh K, Ritchie LD, Robertson C, Sheikh A, McMenamin J. Seasonal Influenza Vaccine Effectiveness (SIVE): an observational retrospective cohort study – exploitation of a unique community-based national-linked database to determine the effectiveness of the seasonal trivalent influenza vaccine. Southampton (UK): NIHR Journals Library; 2013 Nov.

The book is freely available on the PUBMED website. [Free book]