Quercetin is a zinc ionophore, just as hydroxychloroquine and ivermectin are.

They work by allowing zinc to pass into the cells. It's the zinc itself that boosts immunity.

There are plenty of natural foods that also contain quercetin, such as blueberries, grapes, honey, red onions, etc.

As far as zinc goes, beef, lamb, hummus (chickpeas), lentils, dark chocolate, mushrooms, avocado are all decent sources.

I take a zinc supplement as well and have been for months now.