Thus far, the evidence is mixed. The strongest evidence to date is for reduction of cold/respiratory illness symptom severity and duration (in doses of 175–600 mg/day over 2-16 days). However, there is no strong evidence to suggest that elderberry can reduce the risk of contracting a cold or viral infection.[1][2][3][4] In terms of cold prevention under stressful circumstances, a single RCT compared elderberry extract to a placebo when taken at 600 to 900 mg/day for 10 days prior to air travel and 4 to 5 days after. While elderberry was not significantly better than placebo at preventing colds, the elderberry group did experience milder symptoms and shorter colds.[5][3][6] However, when elderberry was taken by both children and adults as a syrup extract (30 mL/day for people aged 12 or younger, 60 mL/day for people over 12 years over 5 days), no reduction in the duration or severity of influenza symptoms was found.[7][8]
The COVID-19 pandemic sparked interest in elderberry for the prevention and treatment of coronaviruses.[9][10][11] The prevailing theories for elderberry’s potential as a COVID-19 therapeutic agent consider the antioxidant activity of anthocyanins, which may either prevent viral action and/or produce anti-inflammatory cytokines to help mitigate the damage the virus can cause.[11][10] However, these theories are based on studies of similar viruses, not the SARS-CoV-2 virus. There is still insufficient evidence to recommend elderberry for treatment or prevention of COVID-19.[9]
Although elderberry extracts have been shown to exhibit antiviral and antimicrobial properties in vitro, clinical research is needed to establish whether elderberry exerts antiviral/antimicrobial effects against any specific pathogens in humans.[12]