Just fyi, the study that debunked echinacea's efficacy was quite flawed - it used about a quarter of the standard recommended dose. It's like saying antibiotics don't work after doing a study using a fraction of the dose for half the recommended duration. Duh!
Garlic is great for immunity. Look for a brand that is high in allicin (one of the active compounds). Better yet, eat a little raw garlic (crushed). Yeah, it's a bit much, but if you're getting sick it'll kick any virus's ass. And cayenne is great too. Astragalus (a Chinese herb) and reishi mushroom are also great for boosting immunity.
But remember, boosting immunity only works if you eat and sleep well - kicking your immune system into overdrive is helpful in a crunch, but you system needs a full tank of gas and plenty of clean oil to keep performing long term.