Cochrane Study: Influenza Vaccine does not affect complication rate

Cochrane Database Syst Rev. 2010 Jul 7;(7):CD001269.

Vaccines for preventing influenza in healthy adults.

Abstract

AUTHORS' CONCLUSIONS: Influenza vaccines have a modest effect in reducing influenza symptoms and working days lost. There is no evidence that they affect complications, such as pneumonia, or transmission. WARNING: This review includes 15 out of 36 trials funded by industry (four had no funding declaration). An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in light of this finding.

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http://www.ncbi.nlm.nih.gov/pubmed/20614424