Rodrigo, C., Leonardi-Bee, J., Nguyen-Van-Tam, J., and Lim, W. (2015). Effect of Corticosteroid Therapy on Influenza-Related Mortality: A Systematic Review and Meta-Analysis. The Journal of Infectious Diseases. 212(2):183-194.
The authors reviewed 16 observational studies and found that corticosteroid therapy for presumed influenza-associated complications is associated with increased mortality. The authors also noted that they were unable to identify any clinical trials on the issue, not all studies specified the indications for corticosteroid therapy, and that when doses were specified they were a higher daily dose than typically recommended.