One of my favorite literature researchers is Richard Bukata.
Here he talks about a marginal benefit for flu.
Tamiflu
http://www.epmonthly.com/www.epmonthly.com/features/current-features/tamiflu-know-the-research-before-you-prescribe/?utm_source=EPM+2014-1-23&utm_campaign=EPM+January+23+2014&utm_medium=email