Two randomized, parallel-group clinical studies with a verum and a control group were performed to investigate the effect of a standardized extract (SHA-10) of Andrographis panaiculata (N.) fixed combination Kan Jang in the treatment of diagnosed influenza viral infection. The pilot study was performed on 540 patients with 71 Kan Jang-treated patients with the second phase conducted enrolling 66 patients. The differences in the duration of sick leave and frequency of post-influenza complications indicate that the Kan Jang phytopreparation not only contributes to quicker recovery, but also reduces the risk of post-influenza complications. Kan Jang was well tolerated by patients.