Supplementing with dried oregano or sage stimulates your innate immune system. This is suggested by a somewhat older American animal study. The innate immune system is the first line of defense against pathogens. When this part of the immune system is functioning optimally, it can deal with viruses and other pathogens without making you sick - and therefore without your adaptive immune system having to be activated.

Study
Biotechnologists at Texas State University published an animal study in 2013 in which they exposed earthworms - in Latin: Lumbricus terrestris - to dried oregano [Origanum vulgare] or dried sage [Salvia officinalis].

The researchers simply mixed the leaves into the soil where the worms lived, allowing the animals to absorb the active ingredients in these two herbs through their gastrointestinal tract.

We don't know how to convert the concentration of dried leaves in the soil to a human dose. We've been fiddling with formulas in a way that is unacceptable in an academic setting. This led us to a rough and irresponsible estimate that a human dose is 1.5 to 2 grams per day.

Results
Before and after six days of exposure, the researchers counted the worms' immune cells (coelomocytes). They also determined the cells' vitality.

Both oregano and sage increased the number and vitality of immune cells. Worms only have an innate immune system. These shifts therefore concern that immune system.

Within this type of immune cell, the number of neutrophil-like coelomocytes increased significantly. Natural killer (NK) cells are among the human equivalents of this type of immune cell.

The researchers observed that sage supplementation, in particular, increased the ability of immune cells to eliminate pathogens with aggressive molecules (respiratory oxidative burst). Supplementation also increased the ability of immune cells to engulf and destroy foreign material (phagocytosis).

Conclusion
"Our results indicate that dietary intake of Lamiaceae herbs (oregano and sage) improved innate immune system functions [...] in vivo", the researchers summarize.

"Lamiaceae herbs may have potential immune-modulatory properties important for human health and merit further investigation."