Relation of study quality, concordance, take home message, funding, and impact in studies of influenza vaccines: systematic review

doi:10.1136/bmj.b354

Published 12 February 2009, doi:10.1136/bmj.b354
Cite this as: BMJ 2009;338:b354

Research

Relation of study quality, concordance, take home message, funding, and impact in studies of influenza vaccines: systematic review

T Jefferson, coordinator, C Di Pietrantonj, statistician, M G Debalini, researcher, A Rivetti, researcher , V Demicheli, director of health, Piemonte region

¹ Cochrane Vaccines Field, ASL (Azienda Sanitaria Locale) AL 20, 15100 Alessandria, Italy

Correspondence to: T Jefferson jefferson.tom{at}gmail.com

Objective To explore the relation between study concordance,take home message, funding, and dissemination of comparativestudies assessing the effects of influenza vaccines.

Design Systematic review without meta-analysis.

Data extraction Search of the Cochrane Library, PubMed, Embase,and the web, without language restriction, for any studies comparingthe effects of influenza vaccines against placebo or no intervention.Abstraction and assessment of quality of methods were carriedout.

Data synthesis We identified 259 primary studies (274 datasets).Higher quality studies were significantly more likely to showconcordance between data presented and conclusions (odds ratio16.35, 95% confidence interval 4.24 to 63.04) and less likelyto favour effectiveness of vaccines (0.04, 0.02 to 0.09). Governmentfunded studies were less likely to have conclusions favouringthe vaccines (0.45, 0.26 to 0.90). A higher mean journal impactfactor was associated with complete or partial industry fundingcompared with government or private funding and no funding (differencesbetween means 5.04). Study size was not associated with concordance,content of take home message, funding, and study quality. Highercitation index factor was associated with partial or completeindustry funding. This was sensitive to the exclusion from theanalysis of studies with undeclared funding.

Conclusion Publication in prestigious journals is associatedwith partial or total industry funding, and this associationis not explained by study quality or size.

© Jefferson et al 2009
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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