Influenza and/or Pneumococcal Vaccination Against Stroke and Transient Ischaemic Attack (IPVASTIA)

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Project title Case-Control Study to Investigate Potential for Influenza and/or Pneumococcal Vaccination to Prevent Against Stroke and Transient Ischaemic Attack (IPVASTIA)
Funding body  National Institute for Health Research (NIHR) – Research for Patient Benefit Programme (Project Ref. No. PB-PG-0808-16254)
Total funding £82,534
Team 
  • Professor Niroshan Siriwardena, Professor of Primary and Pre-hospital Health Care, School of Health & Social Care, University of Lincoln
  • Dr Zahid Asghar, Senior Lecturer, School of Health and Social Care, University of Lincoln
  • Dr Carol Coupland, Associate Professor, University of Nottingham.
Overarching aim We aimed to investigate the association between influenza vaccination (within the last vaccination season), pneumococcal vaccination (ever) or influenza and pneumococcal vaccination combined, with stroke or Transient Ischaemic Attack (TIA) and whether this association was independent of other major cardiovascular risk factors. The usual risk factors such as age, gender, smoking, diabetes and BMI etc., only account for approximately two-thirds of mortality and morbidity.
Objectives 
  • To investigate the association between Cardiovascular Disease (CVD) and winter respiratory infections
  • To quantify the strength of this association (between CVD and seasonal respiratory infections)
  • To assess if preventing influenza, particularly by means of influenza vaccination, can prevent influenza-triggered stroke/TIA.
Methods This was a matched case-control study using the General Practice Research Database (GPRD). Cases included patients (living or dead) recorded with stroke or TIA (fatal or non-fatal) over 96 months. We studied the effect of influenza vaccination given in the season prior to first stroke occurring between September 2001 to August 2009 and/or pneumococcal vaccination given ever. We analysed the risk of stroke and TIA from time of influenza or pneumococcal vaccination with one control for each case, matched for age, sex, calendar time and practice. Cases and controls were aged 18 years or over. We adjusted for confounders including major cardiovascular risk factors, vaccine risk groups, comorbidity and indicators of functional disability. We also undertook sensitivity analyses to estimate the risk of bias in our results. We are now conducting a self controlled case series study using the same dataset.
Outcomes 
  • Influenza vaccination within the same season was associated with a 10 per cent reduction in risk of stroke
  • Sensitivity analysis also showed that a small but significant reduction in risk of stroke with pneumococcal vaccination in patients aged under 65 years was probably due to unmeasured confounding.
Outputs Peer reviewed publications

Conference presentations

Impact 
  • The research has increased public and professional awareness of the potential link between influenza and stroke/TIA and the potential for influenza vaccination to prevent stroke/TIA. The paper in vaccine received worldwide news coverage and which was publicised by the journal Vaccine.
  • It will benefit professional policy and practice, by contributing to better understanding of barriers to vaccination of adults against influenza and S. pneumoniae (a bacterium which causes community acquired pneumonia, meningitis and blood poisoning) and developing and testing methods that can improve vaccination rates in high risk groups.

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