Effect of influenza vaccination on excess deaths occurring during periods of high circulation of influenza: cohort study in elderly peopleBMJ 2004; 329 doi: https://doi.org/10.1136/bmj.38198.594109.AE (Published 16 September 2004) Cite this as: BMJ 2004;329:660
- Ben G Armstrong, reader ()1,
- Punam Mangtani, lecturer1,
- Astrid Fletcher, professor1,
- Sari Kovats, lecturer1,
- Anthony McMichael, professor1,
- Sam Pattenden, lecturer1,
- Paul Wilkinson, senior lecturer1
- Correspondence to: B G Armstrong
- Accepted 6 July 2004
Objective To estimate the protection against death provided by vaccination against influenza.
Design Prospective cohort follow up supplemented by weekly national counts of influenza confirmed in the community.
Setting Primary care.
Participants 24 535 patients aged over 75 years from 73 general practices in Great Britain.
Main outcome measure Death.
Results In unvaccinated members of the cohort daily all cause mortality was strongly associated with an index of influenza circulating in the population (mortality ratio 1.16, 95% confidence interval 1.04 to 1.29 at 90th centile of circulating influenza). The association was strongest for respiratory deaths but was also present for cardiovascular deaths. In contrast, in vaccinated people mortality from any cause was not associated with circulating influenza. The difference in patterns between vaccinated and unvaccinated people could not easily be due to chance (P = 0.02, all causes).
Conclusions This study, using a novel and robust approach to control for confounding, provides robust evidence of a protective effect on mortality of vaccination against influenza.
Details of statistical methods are on bmj.com
We thank the respiratory division of CDSC, Public Health Laboratory Service (since April 2003 the Health Protection Agency) for access to laboratory reports of influenza. AMcM now works at the National Centre for Epidemiology and Population Health, Australian National University, Canberra.
Contributors BGA was involved in study design, statistical analysis, and preparation of the manuscript. PM was involved in collection of data on vaccination and influenza and preparation of the manuscript. AF was involved in study design and was principal investigator for this study and the parent study. SK was involved in collection of data on vaccination, influenza, and weather. AMcM and PW were involved in study design. SP was involved in statistical analysis. All contributors commented on manuscript drafts and participated in study progress meetings. BGA is the guarantor of the paper. He accepts full responsibility for the conduct of the study, had access to the data and controlled the decision to publish in consultation with the other authors.
Funding This study was supported by the UK Medical Research Council. PM was funded by the Wellcome Foundation (grant number 051637) during this work. PW is supported by a public health career scientist award (NHS Executive, CCB/BS/PHCS031).
Competing interests None declared.
Ethical approval The study was approved by the relevant local research ethics committees.