Homeopathic Oscillococcinum® for preventing and treating influenza and influenza-like illness.

BACKGROUND: Influenza is a highly infectious viral disease that is particularly common in the winter months. Oscillococcinum® is a patented homeopathic medicine that is made from a 1% solution of wild duck heart and liver extract, which is then serially diluted 200 times with water and alcohol. OBJECTIVES: To determine whether homeopathic Oscillococcinum® is more effective than placebo in the prevention and/or treatment of influenza and influenza-like illness in adults or children. SEARCH METHODS: We searched CENTRAL (2014, Issue 8), MEDLINE (1966 to August week 4, 2014), MEDLINE In-Process & Other Non-Indexed Citations (4 September 2014), AMED (2006 to September 2014), Web of Science (1985 to September 2014), LILACS (1985 to September 2014) and EMBASE (1980 to September 2014). We contacted the manufacturers of Oscillococcinum® for information on further trials. SELECTION CRITERIA: Randomised, placebo-controlled trials of Oscillococcinum® in the prevention and/or treatment of influenza and influenza-like illness in adults or children. DATA COLLECTION AND ANALYSIS: Three review authors independently extracted data and assessed risk of bias in the eligible trials. MAIN RESULTS: No new trials were included in this 2014 update. We included six studies: two prophylaxis trials (327 young to middle-aged adults in Russia) and four treatment trials (1196 teenagers and adults in France and Germany). The overall standard of trial reporting was poor and hence many important methodological aspects of the trials had unclear risk of bias. There was no statistically significant difference between the effects of Oscillococcinum® and placebo in the prevention of influenza-like illness: risk ratio (RR) 0.48, 95% confidence interval (CI) 0.17 to 1.34, P value = 0.16. Two treatment trials (judged as 'low quality') reported sufficient information to allow full data extraction: 48 hours after commencing treatment, there was an absolute risk reduction of 7.7% in the frequency of symptom relief with Oscillococcinum® compared with that of placebo (risk difference (RD) 0.077, 95% CI 0.03 to 0.12); the RR was 1.86 (95% CI 1.27 to 2.73; P value = 0.001). A significant but lesser effect was observed at three days (RR 1.27, 95% CI 1.03 to 1.56; P value = 0.03), and no significant difference between the groups was noted at four days (RR 1.11, 95% CI 0.98 to 1.27; P value = 0.10) or at five days (RR 1.06, 95% CI 0.96 to 1.16; P value = 0.25). One of the six studies reported one patient who suffered an adverse effect (headache) from taking Oscillococcinum®. AUTHORS' CONCLUSIONS: There is insufficient good evidence to enable robust conclusions to be made about Oscillococcinum® in the prevention or treatment of influenza and influenza-like illness. Our findings do not rule out the possibility that Oscillococcinum® could have a clinically useful treatment effect but, given the low quality of the eligible studies, the evidence is not compelling. There was no evidence of clinically important harms due to Oscillococcinum®.