Maybe not so much placebo with elderberry
Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review - PMC.
Elderberry contains anthocyanins, a subset of flavonoids which may have immunomodulating and possibly anti-inflammatory effects [10]. Anthocyanins can attach to (and render ineffective) viral glycoproteins that enable viruses to enter host cells, thereby potentially having an inhibitory effect on viral infection. Extracts of elderberry have demonstrated in-vitro to have inhibitory effects on influenza A and influenza B viruses [11, 12] as well as H1N1 “swine” flu virus [13]
(Full disclosure, I grow elderberries and prepare syrup for our use, and take it daily.)
