Even if you start taking it while you're sick ( its definitely best to take it as prevention before you get sick though, I take 1 cap everyday, all year round) it will knock it on the head almost instantly..thing to remember is the dosage size, you can get low dosage caps with other stuff added which I find are not nearly as good..
What you want is 5000mg- or 5 grms of pure Olea Europaea - 1 cap a day.
The one I take is also Organic and suitable for vegans.
I definitely want to try this too...