Epidemiology and Infection

Influenza

Rapid assessment of influenza vaccine effectiveness: analysis of an internet-based cohort

K. T. D. EAMESa1 c1, E. BROOKS-POLLOCKa1, D. PAOLOTTIa2, M. PEROSAa2, C. GIOANNINIa2 and W. J. EDMUNDSa1

a1 London School of Hygiene and Tropical Medicine, London, UK

a2 Institute for Scientific Interchange (ISI), Torino, Italy

SUMMARY

The effectiveness of influenza vaccination programmes is seldom known during an epidemic. We developed an internet-based system to record influenza-like symptoms and response to infection in a participating cohort. Using self-reports of influenza-like symptoms and of influenza vaccine history and uptake, we estimated vaccine effectiveness (VE) without the need for individuals to seek healthcare. We found that vaccination with the 2010 seasonal influenza vaccine was significantly protective against influenza-like illness (ILI) during the 2010–2011 influenza season (VE 52%, 95% CI 27–68). VE for individuals who received both the 2010 seasonal and 2009 pandemic influenza vaccines was 59% (95% CI 27–77), slightly higher than VE for those vaccinated in 2010 alone (VE 46%, 95% CI 9–68). Vaccinated individuals with ILI reported taking less time off work than unvaccinated individuals with ILI (3·4 days vs. 5·3 days, P<0·001).

(Accepted August 16 2011)

(Online publication September 12 2011)

Correspondence:

c1 Author for correspondence: Dr K. T. D. Eames, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. (Email: Ken.Eames@lshtm.ac.uk)

Footnotes

† These authors contributed equally to this work.

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