Thorax 67:709-717 doi:10.1136/thoraxjnl-2011-200266
  • Respiratory infection
  • Original article

Predictors of clinical outcome in a national hospitalised cohort across both waves of the influenza A/H1N1 pandemic 2009–2010 in the UK

Open Access
  1. on behalf of the Influenza Clinical Information Network (FLU-CIN)
  1. 1Division of Epidemiology and Public Health, University of Nottingham, Nottingham, UK
  2. 2Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
  3. 3Department of Respiratory Medicine, Nottingham University Hospitals NHS Trust, Nottingham, UK
  4. 4Centre for Respiratory Infections, National Heart and Lung Institute, Imperial College, London, UK
  5. 5Department of Health, Skipton House, London, UK
  6. 6Department of Infection and Immunity, University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK
  7. 7Department of Critical Care, Portsmouth Hospitals NHS Trust, Portsmouth, UK
  8. 8Centre for Peri-operative Medicine and Critical Care Research, Imperial College Healthcare NHS Trust, London, UK
  9. 9Health Protection Scotland, NHS National Services, Glasgow, UK
  10. 10Infectious Diseases Unit, University Hospitals of Leicester NHS Trust, Leicester Royal Infirmary, Leicester, UK
  1. Correspondence to Professor Jonathan S Nguyen-Van-Tam, Clinical Sciences Building, City Hospital, Hucknall Road, Nottingham NG5 1PB, UK; jvt{at}
  1. Contributors All authors were involved with designing the study, interpreting and analysing the data, contributing to the article and approving the final version. JEE trained FLU-CIN data collectors, coordinated data collection, collated the data and oversaw data entry with JSN-V-T. PRM analysed the data. MGS adjusted the paediatric data for age and temperature. PRM, MGS, WSL and JSN-V-T wrote the article with the assistance of all co-authors and JSN-V-T acts as guarantor. The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of their respective employers.

  • Received 28 March 2011
  • Accepted 2 February 2012
  • Published Online First 10 March 2012


Background Although generally mild, the 2009–2010 influenza A/H1N1 pandemic caused two major surges in hospital admissions in the UK. The characteristics of patients admitted during successive waves are described.

Methods Data were systematically obtained on 1520 patients admitted to 75 UK hospitals between May 2009 and January 2010. Multivariable analyses identified factors predictive of severe outcome.

Results Patients aged 5–54 years were over-represented compared with winter seasonal admissions for acute respiratory infection, as were non-white ethnic groups (first wave only). In the second wave patients were less likely to be school age than in the first wave, but their condition was more likely to be severe on presentation to hospital and they were more likely to have delayed admission. Overall, 45% had comorbid conditions, 16.5% required high dependency (level 2) or critical (level 3) care and 5.3% died. As in 1918–1919, the likelihood of severe outcome by age followed a W-shaped distribution. Pre-admission antiviral drug use decreased from 13.3% to 10% between the first and second waves (p=0.048), while antibiotic prescribing increased from 13.6% to 21.6% (p<0.001). Independent predictors of severe outcome were age 55–64 years, chronic lung disease (non-asthma, non-chronic obstructive pulmonary disease), neurological disease, recorded obesity, delayed admission (≥5 days after illness onset), pneumonia, C-reactive protein ≥100 mg/litre, and the need for supplemental oxygen or intravenous fluid replacement on admission.

Conclusions There were demographic, ethnic and clinical differences between patients admitted with pandemic H1N1 infection and those hospitalised during seasonal influenza activity. Despite national policies favouring use of antiviral drugs, few patients received these before admission and many were given antibiotics.


  • PRM and MGS are joint first authors

  • Funding FLU-CIN was supported by the Department of Health, England (principal funder), and the Scottish government Chief Medical Officer and Public Health Directorate in Scotland. Chairmanship of the FLU-CIN Strategy Group that includes JSN-V-T, WSL, MGS, PJMO, RCR, BLT, SJB, JMcM, JEE and KGN as members was provided by the Department of Health, England. The report was approved for publication by the Department of Health, England. All authors had full access to all data in the study. The FLU-CIN Strategy Group had final responsibility for the interpretation of findings and decision to submit for publication.

  • Correction notice This article has been corrected since it was published online first. The following sentence has been updated to read ‘despite the opening of the National Pandemic Flu Service in late July 2009’.

  • Competing interests JS N-V-T has received funding to attend influenza related meetings, lecture and consultancy fees and research funding from several influenza antiviral drug and vaccine manufacturers. All forms of personal remuneration ceased in September 2010, but influenza-related research funding from GlaxoSmithKline, F Hoffmann-La Roche and Astra-Zeneca remains current. He is a former employee of SmithKline Beecham plc (now GlaxoSmithKline), Roche Products Ltd, and Aventis-Pasteur MSD (now Sanofi-Pasteur MSD), all prior to 2005, with no outstanding pecuniary interests by way of shareholdings, share options or accrued pension rights. PRM holds an unrestricted educational grant from F Hoffman-La Roche Ltd for research in the area of pandemic influenza. RCR has received funding for vaccine-related research from Novartis and travel funding from GlaxoSmithKline. EMG and CA are employees of the Department of Health, England; EMG has received one-off support for travel and accommodation (without fees) from Solvay (now Abbott) to give a lecture at an educational meeting on influenza. BB provides clinical advice to the Department of Health, England under non-personal consultancy terms. WSL has received unrestricted funding from Pfizer (previously Wyeth) for research in the area of pneumonia. MGS is an advisor to the Department of Health, England. SJB has received consultancy fees from GlaxoSmithKline and Baxter. JEE has received consultancy fees from GlaxoSmithKline, has performed paid work for the Department of Health, England and holds an unrestricted educational grant from Astra-Zeneca for influenza-related research. KGN has received H5 avian influenza vaccines from Novartis and H1N1 pandemic influenza vaccines from GlaxoSmithKline and Baxter to facilitate MRC and NIHR-funded trials. He has received consultancy fees from Novartis and GlaxoSmithKline and lecture fees from Baxter. A colleague of KGN at the University Hospitals of Leicester NHS Trust was Principal Investigator and recipient of research funding from Roche on antiviral resistance and from Novartis on pandemic H1N1 vaccines. All authors have completed the unified competing interest form at (available on request from the corresponding author).

  • Ethics approval Before commencement, FLU-CIN procedures were reviewed by the Ethics and Confidentiality Committee of the National Information Governance Board for Health and Social Care in England and approved for collection, storage and use of personal data for surveillance purposes.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement The collection of data for the FLU-CIN database has been publicly funded and, as a public good, will be made available for new research purposes on a case-by-case basis. In general, only anonymised data will be supplied to researchers, except where the law permits the processing of identifiable data. Ownership and oversight of data access and use resides with the Pandemic Influenza Preparedness Team at the Department of Health, England. Any requests for access to FLU-CIN data should be made to Department of Health via the corresponding author, Prof JS Nguyen-Van-Tam.

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