Date	Event	Description
4 July 2008	Amended	Converted to new review format.
22 March 2007	New citation required and conclusions have changed	In this 2007 updated review we added "to assess the effectiveness of Chinese medicinal herbs in preventing cases of influenza" in the Objectives section because Chinese medicinal herbs are also commonly used for preventing influenza during epidemic periods. We excluded quasi‐RCTs. We interviewed the trial authors and excluded any supposed RCTs which we discovered were in fact not randomised controlled trials. We excluded comparisons of one herbal medicine with another herbal medicine as we were uncertain of the control herb's efficacy. Accordingly, the references to studies were changed and new trials were found. We also changed the types of outcome measures because we added prophylactic studies and continuous data for analyses. As a result, the 'Description of studies', 'Risk of bias in included studies', 'Results' and 'Discussion' sections were amended.
28 October 2004	New search has been performed	Searches conducted.