Fourteen RCTs (n=unknown) were included. Three RCTs scored a maximum of 5 points on the Jadad scale, three RCTs scored 4 points, two RCTs scored three points, five RCTs scored two points and one RCT scored one point.
Treatment (10 RCTs):
A greater improvement in symptoms (one RCT, n=40), and a reduction of the duration of symptoms by four days (one RCT, n=60), was reported for participants treated with Sambucus nigra compared to placebo. A high dose of Echinacea purpurea extract (900mg) was found to be more beneficial than placebo for symptom reduction at 3, 4, 8 and 10 days (one RCT, n=120). However, no significant differences were found comparing a lower dose of Echinacea purpurea extract (450mg) and placebo. Responder rates for complete symptom resolution within 48 hours (two RCTs, n=850) were greater for Oscillococcinum use compared to placebo and there was also a beneficial effect on duration of symptoms (two RCTs, n=850); no evidence of statistical heterogeneity was found for this analysis.
There was a significantly lower risk of participants using Kan Jang developing secondary infection-induced complications compared to an active comparator and a reduction in sick leave (one RCT, n=66). Responder rates for symptom resolution within 48 hours was significantly higher for participants treated with Gan Mao Jiao Nan in comparison with Amantadine (one RCT, n=213).
Prevention (four RCTs):
Fewer cases were reported of influenza for participants receiving Panax quinquefolium compared with placebo (two RCTs, n=198), or Gan Mao Jiao Nan compared to Amantadine (one RCT, n=738). No statistically significant differences were found between Oscillococcinum or placebo groups for the incidence of influenza-like illness (one RCT, n=1,573) or between Mucococcinum and placebo groups for number of reported symptoms (one RCT).
There were a high number of incidents of adverse events reported for Panax quinquefolium. Fifty percent of these adverse events were gastrointestinal symptoms and were mainly mild to moderate in severity and some serious adverse events were not related to trial medication (one RCT). There was a significantly higher incidence of adverse events in the Oscillococcinum group compared to placebo (one RCT). No adverse events were observed in three trials and the remaining trials did not monitor adverse events.